Added

• Navigation API
  to web-sys #5247

• Added riscv64gc-unknown-linux-gnu release artifacts.
  #5265

• Added JsNullable<T>, modeling WebIDL nullable types (T | null). Both
  null and undefined are treated as absent, per WebIDL's ECMAScript
  conversion rules; the canonical empty value produced from Rust is null.
  web-sys now uses JsNullable<T> instead of JsOption<T> for nullable
  types nested inside generics (e.g. Promise<GpuError?> from
  GPUDevice.popErrorScope()), fixing spec-defined null resolutions being
  treated as present values under JsOption<T>'s strict undefined-only
  semantics. JsNullable<T> participates in the same upcast lattice as
  JsOption<T> (including contravariant closure argument casts), and
  additionally upcasts from Null and from JsOption<T> itself. Imported
  extern types now also upcast into JsOption<JsValue> and
  JsNullable<JsValue>, so catch-all nullable closures can be used where a
  typed callback is expected.
  #5234

Changed

• Emscripten output now marks public exports (free functions, classes, enums,
  and namespace roots) with the __export: true and __force: true symbol
  attributes on their addToLibrary entries, instead of mutating
  EXPORTED_FUNCTIONS and pushing to extraLibraryFuncs at library-load time.
  The $initBindgen init closure is kept via __force: true, and private
  symbols (including namespace leaves) carry neither attribute — they remain
  reachable through __deps. Requires an emscripten with __export/__force
  symbol-attribute support.

• Updated WebGPU bindings to the August 2026 spec, including the new
  GPUCommandEncoder::copy_buffer_to_buffer overloads and setImmediates.
  #5246

• Unstable API overload names now elide name tokens shared by every overload
  variant: LockManager::request_with_callback is now request, and
  request_with_options_and_callback is now request_with_options.
  #5246

Fixed

• The name property of the JS error thrown for panic=unwind is now set from
  a string literal instead of PanicError.name, so it survives minification.
  #5260

• Fixed Emscripten builds using pthreads failing to link.
  #5254

• __wbg_load in web targets now throws a clear error including the HTTP
  status and URL when given a non-ok fetch Response, instead of surfacing a
  misleading MIME-type or Wasm-magic-number error.
  #5256

• Restored __stack_pointer when an exception unwinds out of a wasm export,
  preventing repeated panic = "unwind" calls from leaking shadow-stack frames
  until the shadow stack is exhausted and calls trap. Node reports
  memory access out of bounds; poisoned instances can instead report
  Module terminated.
  #5244

• slice_to_array on a &mut slice (which silently discarded JS's writes) or
  on a slice with a generic element type is now a compile error, and strings
  and arrays received by JS (e.g. a Vec<String> return value) no longer make
  a redundant copy of the freshly built value.
  #5261

• Fixed async imports with non-JS-handle resolved types (e.g.
  async fn f() -> u32;) silently producing garbage since 0.2.109: the
  descriptor named the resolved type instead of the Promise handle that
  actually crosses the ABI.
  #5249

• Fixed catch imports returning i64/u64 throwing a TypeError (and
  panicking in __wbindgen_exn_store) when the JS import throws, since the
  handleError catch path returned undefined which cannot be converted to
  a Wasm i64.
  #5238

• js_namespace is now part of an imported function's and imported static's
  generated shim name. Two imports with identical Rust signatures that differed
  only in their js_namespace hashed to the same __wbg_<name>_<hash>
  symbol, so they were treated as one binding and one of the two call sites
  silently invoked the wrong JS value.
  #5250

• Macro hygiene fixes - slice_to_array now works in #![no_std] crates.
  Generated code no longer names core or std unqualified.
  #5251

• Fixed length prefixes in descriptor strings to count chars rather than
  UTF-8 bytes, so non-ASCII names in js_name/typescript_type no longer
  panic the CLI or mis-bind the generated bindings.
  #5248

• Fixed threaded Wasm memory layout to reserve wasm-bindgen's internal thread
  page after the module's original initial memory instead of at __heap_base,
  avoiding overlap with allocators that resolve __heap_base/__heap_end at
  link time and treat that range as preexisting heap space.
  #5225

• Emscripten output now reaches wasm exports through emscripten's wasmExports
  object using bracket (string-literal) access (wasmExports['__wbindgen_start'])
  instead of a local wasm alias with dot access. wasmExports['name'] is the
  form emcc's DCE graph roots and its import/export minifier renames in the JS
  and the wasm together, so the glue now survives and stays consistent under
  -O3/-Os (previously the export names were minified without updating the JS
  call sites, e.g. __wbindgen_start is not defined).

• The emscripten detection marker static is no longer leaked as public API.
  #5220
  #5222

Added

• Navigation API to web-sys #5247

• Added #[wasm_bindgen(generic_per_mono)] for imported functions, which binds a generic import once per monomorphisation instead of erasing its type parameters to JsValue. It can be applied to an individual import or to a whole extern "C" block, which every function in the block then inherits. Each instantiation gets its own descriptor, so arguments and return values are marshalled at their concrete types (a u32 crosses as a number, a String as a string) rather than being boxed. Trait bounds, where predicates (including higher-ranked ones), associated-type projections, lifetime parameters, async, catch, and slice_to_array are all supported; see the guide for the supported surface and the shapes that are rejected.

• Added riscv64gc-unknown-linux-gnu release artifacts. #5265

• Added JsNullable<T>, modeling WebIDL nullable types (T | null). Both null and undefined are treated as absent, per WebIDL's ECMAScript conversion rules; the canonical empty value produced from Rust is null. web-sys now uses JsNullable<T> instead of JsOption<T> for nullable types nested inside generics (e.g. Promise<GpuError?> from GPUDevice.popErrorScope()), fixing spec-defined null resolutions being treated as present values under JsOption<T>'s strict undefined-only semantics. JsNullable<T> participates in the same upcast lattice as JsOption<T> (including contravariant closure argument casts), and additionally upcasts from Null and from JsOption<T> itself. Imported extern types now also upcast into JsOption<JsValue> and JsNullable<JsValue>, so catch-all nullable closures can be used where a typed callback is expected. #5234

• Added experimental JSPI (JS Promise Integration) support: using it emits a compiler warning noting the experimental status. Supports #[wasm_bindgen(jspi)] on exports (sync or async), within which a #[wasm_bindgen(suspending)] import call can suspend to the JS event loop until its Promise settles. js_sys::futures::jspi_block_on_promise also suspends on any Promise inside a synchronous function, while spawn_local is context-aware: tasks spawned from within a JSPI context support synchronous JSPI suspensions throughout their call trees. Compatible with catch (rejections as Err), async, and panic=unwind. #5193

Changed

• Emscripten output now marks public exports (free functions, classes, enums, and namespace roots) with the __export: true and __force: true symbol attributes on their addToLibrary entries, instead of mutating EXPORTED_FUNCTIONS and pushing to extraLibraryFuncs at library-load time. The $initBindgen init closure is kept via __force: true, and private symbols (including namespace leaves) carry neither attribute — they remain reachable through __deps. Requires an emscripten with __export/__force symbol-attribute support.

• Updated WebGPU bindings to the August 2026 spec, including the new GPUCommandEncoder::copy_buffer_to_buffer overloads and setImmediates. #5246

• Unstable API overload names now elide name tokens shared by every overload variant: LockManager::request_with_callback is now request, and request_with_options_and_callback is now request_with_options. #5246

Fixed

• The name property of the JS error thrown for panic=unwind is now set from a string literal instead of PanicError.name, so it survives minification. #5260

• Fixed Emscripten builds using pthreads failing to link. #5254

• __wbg_load in web targets now throws a clear error including the HTTP status and URL when given a non-ok fetch Response, instead of surfacing a misleading MIME-type or Wasm-magic-number error. #5256

• Restored __stack_pointer when an exception unwinds out of a wasm export, preventing repeated panic = "unwind" calls from leaking shadow-stack frames until the shadow stack is exhausted and calls trap. Node reports memory access out of bounds; poisoned instances can instead report Module terminated. #5244

• slice_to_array on a &mut slice (which silently discarded JS's writes) or on a slice with a generic element type is now a compile error, and strings and arrays received by JS (e.g. a Vec<String> return value) no longer make a redundant copy of the freshly built value. #5261

• Fixed async imports with non-JS-handle resolved types (e.g. async fn f() -> u32;) silently producing garbage since 0.2.109: the descriptor named the resolved type instead of the Promise handle that actually crosses the ABI. #5249

• Fixed catch imports returning i64/u64 throwing a TypeError (and panicking in __wbindgen_exn_store) when the JS import throws, since the handleError catch path returned undefined which cannot be converted to a Wasm i64. #5238

• js_namespace is now part of an imported function's and imported static's generated shim name. Two imports with identical Rust signatures that differed only in their js_namespace hashed to the same __wbg_<name>_<hash> symbol, so they were treated as one binding and one of the two call sites silently invoked the wrong JS value. #5250

• Macro hygiene fixes - slice_to_array now works in #![no_std] crates. Generated code no longer names core or std unqualified. #5251

• Fixed length prefixes in descriptor strings to count chars rather than UTF-8 bytes, so non-ASCII names in js_name/typescript_type no longer panic the CLI or mis-bind the generated bindings. #5248

• Fixed threaded Wasm memory layout to reserve wasm-bindgen's internal thread page after the module's original initial memory instead of at __heap_base, avoiding overlap with allocators that resolve __heap_base/__heap_end at link time and treat that range as preexisting heap space. #5225

• Emscripten output now reaches wasm exports through emscripten's wasmExports object using bracket (string-literal) access (wasmExports['__wbindgen_start']) instead of a local wasm alias with dot access. wasmExports['name'] is the form emcc's DCE graph roots and its import/export minifier renames in the JS and the wasm together, so the glue now survives and stays consistent under -O3/-Os (previously the export names were minified without updating the JS call sites, e.g. __wbindgen_start is not defined).

• The emscripten detection marker static is no longer leaked as public API. #5220 #5222

0.2.127 Latest

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Changed

• Emscripten output now hoists every clean export (free functions, classes,
  enums, plus their finalization registries and string-enum tables) out of the
  $initBindgen init closure into its own top-level addToLibrary symbol and
  self-registers it into EXPORTED_FUNCTIONS. emscripten then emits the clean
  API (add, Counter, ...) as named ESM exports under -sMODULARIZE=instance
  and as Module.<name> properties (via each symbol's __postset) in factory
  mode, with no extra sidecar files. Namespaced exports are reached through
  their namespace root (e.g. app), assembled in the root symbol's __postset.
  User module/inline-js imports are now wired as addToLibrary shims (they were
  previously dropped, since emcc resolves imports only against env), and their
  ESM-imported bindings are __wbg_-prefixed to avoid colliding with emcc
  runtime names such as Module/HEAP8.
  #5210

Fixed

• The descriptor interpreter now follows emscripten invoke_* trampolines.
  emscripten's exception/longjmp lowering rewrites direct calls into indirect
  calls through the function table wrapped in imported invoke_*(fnptr, ..args)
  helpers, including the describe helpers a descriptor function must reach. The
  interpreter resolves fnptr against the reconstructed function table, forwards
  the trailing arguments, and evaluates the surrounding "did it throw?" control
  flow (if/else, loop, br_table), so descriptors are interpreted
  correctly on emscripten builds with unwinding/longjmp enabled.
  #5215

• Relaxed alignment requirement for 8-byte types.
  #5204

Changed

• Emscripten output now hoists every clean export (free functions, classes, enums, plus their finalization registries and string-enum tables) out of the $initBindgen init closure into its own top-level addToLibrary symbol and self-registers it into EXPORTED_FUNCTIONS. emscripten then emits the clean API (add, Counter, ...) as named ESM exports under -sMODULARIZE=instance and as Module.<name> properties (via each symbol's __postset) in factory mode, with no extra sidecar files. Namespaced exports are reached through their namespace root (e.g. app), assembled in the root symbol's __postset. User module/inline-js imports are now wired as addToLibrary shims (they were previously dropped, since emcc resolves imports only against env), and their ESM-imported bindings are __wbg_-prefixed to avoid colliding with emcc runtime names such as Module/HEAP8. #5210

Fixed

• The descriptor interpreter now follows emscripten invoke_* trampolines. emscripten's exception/longjmp lowering rewrites direct calls into indirect calls through the function table wrapped in imported invoke_*(fnptr, ..args) helpers, including the describe helpers a descriptor function must reach. The interpreter resolves fnptr against the reconstructed function table, forwards the trailing arguments, and evaluates the surrounding "did it throw?" control flow (if/else, loop, br_table), so descriptors are interpreted correctly on emscripten builds with unwinding/longjmp enabled. #5215

• Relaxed alignment requirement for 8-byte types. #5204

• Fixed compilation with (feature = "std", panic = "unwind", target_feature = "atomics") and prevented a Task leak when a future unwinds out of poll (via a Rust panic or a foreign JS exception) in both the single-threaded and multi-threaded executors. #5214

• Headless Chrome/Edge tests now surface the WebDriver's own error message when session creation fails (e.g. a chromedriver/Chrome version mismatch) instead of a confusing http status: 404. #5211

Removed

0.2.126

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Added

• Added the --force-enable-abort-handler CLI flag, which emits the hard-abort
  detection and set_on_abort machinery on panic=abort builds. With
  panic=unwind this machinery is generated automatically; the flag does
  nothing there.
  #5191

Changed

• Made the internal __wbindgen_destroy_closure export private in the Rust API.
  #5196

Added

• Added the --force-enable-abort-handler CLI flag, which emits the hard-abort detection and set_on_abort machinery on panic=abort builds. With panic=unwind this machinery is generated automatically; the flag does nothing there. #5191

Changed

• Made the internal __wbindgen_destroy_closure export private in the Rust API. #5196

0.2.125

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Added

• Added the maxAge attribute to the CookieInit dictionary in web-sys,
  matching the current Cookie Store API specification.
  #5169

• The js-sys futures codegen opt-in can now also be enabled via the
  WASM_BINDGEN_USE_JS_SYS=1 environment variable, in addition to
  --cfg=wasm_bindgen_use_js_sys. This works on stable when --target
  is in use, where Cargo does not propagate the cfg to host proc-macros.
  #5164

Changed

• JsOption<T> now treats only undefined as empty, aligning it with
  TypeScript's strict T | undefined semantics and with Option<T>'s wire
  shape (None ↔ undefined). Previously is_empty, as_option,
  into_option, unwrap, expect, unwrap_or_default, and
  unwrap_or_else treated both null and undefined as absent; JS null
  is now a distinct present value. The impl<T> UpcastFrom<Null> for JsOption<T> is removed (Undefined still models absence), and the
  Debug/Display absent placeholder changed from "null" to
  "undefined". Code relying on null → None should return undefined
  from the JS side, or check explicitly with
  val.as_option().filter(|v| !v.is_null()).
  #5170

Fixed

• Removed invalid js_sys::Array<T> to js_sys::ArrayTuple<(...)> upcasts.
  ArrayTuple encodes a fixed tuple arity, while a plain JavaScript array does
  not prove that arity statically.

• Fixed incorrect variance in &mut reference upcasting. &mut T upcasts
  were covariant in the pointee, so a &mut T could be widened to a &mut
  of a supertype and used to write back a value the original type would not
  accept, leaving a reference whose static type no longer matches the value
  it points to. Mutable references are now invariant in their pointee:
  &mut T only upcasts to &mut Target when both Target: UpcastFrom<T>
  and T: UpcastFrom<Target> hold. This rejects the invalid widening but is
  a breaking change for callers that relied on widening &mut references.
  #5176

• Fixed WASI targets (wasm32-wasip1/wasm32-wasip2) emitting unresolved
  __wbindgen_placeholder__ imports, which broke component linking. The
  codegen and runtime gates now exclude target_os = "wasi" (restoring the
  pre-0.2.115 stub behavior), including the panic = "unwind" paths in
  wasm-bindgen-futures.
  #5175

• Fixed a panic ("Unhandled load width 8") in the descriptor interpreter when
  processing -Cinstrument-coverage-instrumented modules, unblocking
  cargo llvm-cov --target wasm32-unknown-unknown for crates whose describe
  helpers get instrumented.
  #5179

• Fixed main silently never running on wasm64 for bin crates.
  #5181

Added

• Added the maxAge attribute to the CookieInit dictionary in web-sys, matching the current Cookie Store API specification. #5169

• The js-sys futures codegen opt-in can now also be enabled via the WASM_BINDGEN_USE_JS_SYS=1 environment variable, in addition to --cfg=wasm_bindgen_use_js_sys. This works on stable when --target is in use, where Cargo does not propagate the cfg to host proc-macros. #5164

Changed

• JsOption<T> now treats only undefined as empty, aligning it with TypeScript's strict T | undefined semantics and with Option<T>'s wire shape (None ↔ undefined). Previously is_empty, as_option, into_option, unwrap, expect, unwrap_or_default, and unwrap_or_else treated both null and undefined as absent; JS null is now a distinct present value. The impl<T> UpcastFrom<Null> for JsOption<T> is removed (Undefined still models absence), and the Debug/Display absent placeholder changed from "null" to "undefined". Code relying on null → None should return undefined from the JS side, or check explicitly with val.as_option().filter(|v| !v.is_null()). #5170

Fixed

• Removed invalid js_sys::Array<T> to js_sys::ArrayTuple<(...)> upcasts. ArrayTuple encodes a fixed tuple arity, while a plain JavaScript array does not prove that arity statically.

• Fixed incorrect variance in &mut reference upcasting. &mut T upcasts were covariant in the pointee, so a &mut T could be widened to a &mut of a supertype and used to write back a value the original type would not accept, leaving a reference whose static type no longer matches the value it points to. Mutable references are now invariant in their pointee: &mut T only upcasts to &mut Target when both Target: UpcastFrom<T> and T: UpcastFrom<Target> hold. This rejects the invalid widening but is a breaking change for callers that relied on widening &mut references. #5176

• Fixed WASI targets (wasm32-wasip1/wasm32-wasip2) emitting unresolved __wbindgen_placeholder__ imports, which broke component linking. The codegen and runtime gates now exclude target_os = "wasi" (restoring the pre-0.2.115 stub behavior), including the panic = "unwind" paths in wasm-bindgen-futures. #5175

• Fixed a panic ("Unhandled load width 8") in the descriptor interpreter when processing -Cinstrument-coverage-instrumented modules, unblocking cargo llvm-cov --target wasm32-unknown-unknown for crates whose describe helpers get instrumented. #5179

• Fixed main silently never running on wasm64 for bin crates. #5181

0.2.123

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Notices

• Threading support now requires -Clink-arg=--export=__heap_base to be set
  in RUSTFLAGS for nightly toolchains from 2026-05-06 onward, after
  rust-lang/rust#156174
  removed the implicit __heap_base/__data_end exports on wasm*
  targets. Atomics CI, CLI reference tests, and the nodejs-threads,
  raytrace-parallel, and wasm-audio-worklet examples have been
  updated to pass --export=__heap_base explicitly. The flag is
  backward-compatible with older nightlies.

• -Cpanic=unwind on wasm targets now emits modern (exnref) exception
  handling by default after
  rust-lang/rust#156061,
  and requires Node.js 22.22.3+ (for WebAssembly.JSTag). Legacy EH wasm
  can still be produced on current nightlies by adding
  -Cllvm-args=-wasm-use-legacy-eh to RUSTFLAGS; Node.js 20 may be
  supported with legacy exception handling, with a tracking issue in
  #5151.

Added

• Implemented TryFromJsValue for Vec<T> where T: TryFromJsValue.
  A JS value converts when it is a real Array (per Array.isArray)
  and every element converts via T::try_from_js_value. This composes
  recursively (Vec<Vec<String>>, Vec<Option<T>>) and works for any
  T with a TryFromJsValue impl, including primitives, String,
  JsValue, and JsCast types. Array-likes (objects with length and
  numeric indices) are intentionally rejected to mirror the static ABI
  representation used by js_value_vector_from_abi.

• New extends_js_class and extends_js_namespace attributes on
  exported structs to allow defining the parent js_class name when
  it has been customized by js_name and the parent's own js_namespace
  as well in turn. New validation is added at code generation time that
  will now catch these cases instead of emitting invalid code. Example:

  #[wasm_bindgen(js_name = "Animal", js_namespace = zoo)]
  pub struct AnimalImpl { /* ... */ }
  
  #[wasm_bindgen(
      extends = AnimalImpl,
      extends_js_class = "Animal",
      extends_js_namespace = zoo,
  )]
  pub struct DogImpl { /* ... */ }

  #5154

Changed

• When an exported struct uses js_namespace, the corresponding value
  must now be repeated on every impl block. Previously the impl-side
  defaults silently worked resulting in inconsistent emission. Example:

  // Before:
  #[wasm_bindgen(js_namespace = "default")]
  pub struct Counter { /* ... */ }
  
  #[wasm_bindgen]              // worked, but fragile
  impl Counter { /* ... */ }
  
  // After:
  #[wasm_bindgen(js_namespace = "default")]
  pub struct Counter { /* ... */ }
  
  #[wasm_bindgen(js_namespace = "default")]   // now required
  impl Counter { /* ... */ }

  To ease this transition for js_namespace usage, diagnostic
  messages now include hints for missing namespaces for easier
  fixing.

  #5154

Fixed

• Fixed the descriptor interpreter panicking on Br and BrIf
  instructions emitted by recent nightly compilers when building with
  panic=unwind.
  #5158

• Emscripten output now works against vanilla upstream emscripten without
  requiring a fork. Dependency tracking, HEAP_DATA_VIEW setup,
  function-decl intrinsic inlining, catch-wrapper gating, and imported
  global handling have all been corrected; ESM imports
  (#[wasm_bindgen(module = "...")] and snippets) are emitted to a
  sidecar library_bindgen.extern-pre.js consumers pass to emcc via
  --extern-pre-js; namespaced exports (js_namespace = [...] on a
  struct/impl) now attach to Module.<segments> instead of emitting
  top-level export const (which emcc's library evaluator rejects);
  the generated .d.ts for namespaced exports is now valid TypeScript
  (mangled identifiers stay module-internal via declare class /
  declare enum / declare function plus export { BindgenModule };
  to mark the file as a module; no spurious unqualified Calc:
  property on BindgenModule for namespaced items; namespace shapes
  land as plain interface members (app: { math: { Calc: typeof app__math__Calc } };) instead of the previously-emitted export let app: { ... }; which was invalid TS1131 syntax inside an
  interface body).
  #5156

• Fixed a duplicate phantom class being emitted for an exported struct
  renamed via js_name (Rust ident != JS class name) and/or placed in a
  js_namespace, when the struct crosses the boundary as a JsValue
  (e.g. via .into()). The WrapInExportedClass / UnwrapExportedClass
  imports were keyed by the Rust ident rather than the qualified JS name
  that exported_classes is keyed by (a regression from #5154), so a
  fresh empty class entry was minted and emitted alongside the real one,
  with a free() referencing a nonexistent wasm export. Riding the
  same release's #5154 wire-format bump, the now-vestigial rust_name
  field is dropped from the schema and the namespace-qualified name is
  no longer cached on AuxStruct, AuxEnum, or ExportedClass
  (derived on demand from (name, js_namespace)), collapsing three
  fallback chains that only papered over the pre-#5154 keying.

  #5160

Notices

• Threading support now requires -Clink-arg=--export=__heap_base to be set in RUSTFLAGS for nightly toolchains from 2026-05-06 onward, after rust-lang/rust#156174 removed the implicit __heap_base/__data_end exports on wasm* targets. Atomics CI, CLI reference tests, and the nodejs-threads, raytrace-parallel, and wasm-audio-worklet examples have been updated to pass --export=__heap_base explicitly. The flag is backward-compatible with older nightlies.

• -Cpanic=unwind on wasm targets now emits modern (exnref) exception handling by default after rust-lang/rust#156061, and requires Node.js 22.22.3+ (for WebAssembly.JSTag). Legacy EH wasm can still be produced on current nightlies by adding -Cllvm-args=-wasm-use-legacy-eh to RUSTFLAGS; Node.js 20 may be supported with legacy exception handling, with a tracking issue in #5151.

Added

• Implemented TryFromJsValue for Vec<T> where T: TryFromJsValue. A JS value converts when it is a real Array (per Array.isArray) and every element converts via T::try_from_js_value. This composes recursively (Vec<Vec<String>>, Vec<Option<T>>) and works for any T with a TryFromJsValue impl, including primitives, String, JsValue, and JsCast types. Array-likes (objects with length and numeric indices) are intentionally rejected to mirror the static ABI representation used by js_value_vector_from_abi.

• New extends_js_class and extends_js_namespace attributes on exported structs to allow defining the parent js_class name when it has been customized by js_name and the parent's own js_namespace as well in turn. New validation is added at code generation time that will now catch these cases instead of emitting invalid code. Example:

  #[wasm_bindgen(js_name = "Animal", js_namespace = zoo)]
  pub struct AnimalImpl { /* ... */ }
  
  #[wasm_bindgen(
      extends = AnimalImpl,
      extends_js_class = "Animal",
      extends_js_namespace = zoo,
  )]
  pub struct DogImpl { /* ... */ }
  

  #5154

Changed

• When an exported struct uses js_namespace, the corresponding value must now be repeated on every impl block. Previously the impl-side defaults silently worked resulting in inconsistent emission. Example:

  // Before:
  #[wasm_bindgen(js_namespace = "default")]
  pub struct Counter { /* ... */ }
  
  #[wasm_bindgen]              // worked, but fragile
  impl Counter { /* ... */ }
  
  // After:
  #[wasm_bindgen(js_namespace = "default")]
  pub struct Counter { /* ... */ }
  
  #[wasm_bindgen(js_namespace = "default")]   // now required
  impl Counter { /* ... */ }
  

  To ease this transition for js_namespace usage, diagnostic messages now include hints for missing namespaces for easier fixing.

  #5154

Fixed

• Fixed the descriptor interpreter panicking on Br and BrIf instructions emitted by recent nightly compilers when building with panic=unwind. #5158

• Emscripten output now works against vanilla upstream emscripten without requiring a fork. Dependency tracking, HEAP_DATA_VIEW setup, function-decl intrinsic inlining, catch-wrapper gating, and imported global handling have all been corrected; ESM imports (#[wasm_bindgen(module = "...")] and snippets) are emitted to a sidecar library_bindgen.extern-pre.js consumers pass to emcc via --extern-pre-js; namespaced exports (js_namespace = [...] on a struct/impl) now attach to Module.<segments> instead of emitting top-level export const (which emcc's library evaluator rejects); the generated .d.ts for namespaced exports is now valid TypeScript (mangled identifiers stay module-internal via declare class / declare enum / declare function plus export { BindgenModule }; to mark the file as a module; no spurious unqualified Calc: property on BindgenModule for namespaced items; namespace shapes land as plain interface members (app: { math: { Calc: typeof app__math__Calc } };) instead of the previously-emitted export let app: { ... }; which was invalid TS1131 syntax inside an interface body). #5156

• Fixed a duplicate phantom class being emitted for an exported struct renamed via js_name (Rust ident != JS class name) and/or placed in a js_namespace, when the struct crosses the boundary as a JsValue (e.g. via .into()). The WrapInExportedClass / UnwrapExportedClass imports were keyed by the Rust ident rather than the qualified JS name that exported_classes is keyed by (a regression from #5154), so a fresh empty class entry was minted and emitted alongside the real one, with a free() referencing a nonexistent wasm export. Riding the same release's #5154 wire-format bump, the now-vestigial rust_name field is dropped from the schema and the namespace-qualified name is no longer cached on AuxStruct, AuxEnum, or ExportedClass (derived on demand from (name, js_namespace)), collapsing three fallback chains that only papered over the pre-#5154 keying.

  #5160

0.2.122

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Added

• Added the slice_to_array attribute for imported JS functions,
  which makes a &[T] (or Option<&[T]>) argument arrive on the JS
  side as a plain Array rather than a typed array — without
  changing the Rust-side &[T] signature. Useful when binding JS
  APIs that take T[] rather than TypedArray<T>. For primitive
  element kinds the wire is the same zero-copy borrow used by plain
  &[T], with the JS-side shim wrapping the view in Array.from(...)
  to materialise the Array — no extra allocation. For String,
  JsValue, and JS-imported element types the Rust side builds a
  fresh [u32] index buffer that JS reads and frees, with per-element
  &T -> JsValue (refcount bump for handle-shaped types). No T: Clone bound is required. The attribute can be set per-fn
  (#[wasm_bindgen(slice_to_array)] fn ...) or per-block on an
  extern "C" { ... } declaration to apply to every imported function
  in that block. &[ExportedRustStruct] remains unsupported (use
  owned Vec<T> for that). Has no effect on exported functions;
  default &[T] (typed-array view / memory borrow) and owned
  Vec<T> semantics are unchanged for callers that didn't opt in.
  See the
  slice_to_array guide page.
  #5145

• Added js_sys::AggregateError bindings (constructor, errors getter, and
  new_with_message / new_with_options overloads). AggregateError represents
  multiple unrelated errors wrapped in a single error, e.g. as thrown by
  Promise.any when all input promises reject, along with js_sys::ErrorOptions,
  accepted by built-in error constructors. ErrorOptions::new(cause)
  constructs an instance pre-populated with cause, and get_cause /
  set_cause provide typed access to the property. All standard error
  constructors that previously took only a message (EvalError,
  RangeError, ReferenceError, SyntaxError, TypeError, URIError,
  WebAssembly.CompileError, WebAssembly.LinkError,
  WebAssembly.RuntimeError) now expose a new_with_options(message, &ErrorOptions) overload, and Error gains
  new_with_error_options(message, &ErrorOptions) alongside the existing
  untyped new_with_options. AggregateError::new_with_options also takes
  &ErrorOptions.
  #5139

• Added inheritance for Rust-exported types: an exported struct may
  declare #[wasm_bindgen(extends = Parent)] to inherit from another
  exported #[wasm_bindgen] struct. The macro injects a hidden
  parent: wasm_bindgen::Parent<Parent> field (a refcounted cell around
  the parent value) and emits class Child extends Parent in the
  generated JS / .d.ts. The child gets an AsRef<Parent<Parent>> impl
  for the direct parent, and threads per-class pointer slots through
  the wasm ABI so that instanceof Parent is true and parent methods
  dispatch soundly via the JS prototype chain. From inside child
  methods, parent data is reached via self.parent.borrow() /
  self.parent.borrow_mut(). See the new
  extends guide page.
  #5120

• Added js_sys::FinalizationRegistry bindings (constructor, register,
  register_with_token, and unregister). The cleanup callback parameter
  is typed as &Function<fn(JsValue) -> Undefined>, so closures created via
  Closure::new can be passed using Function::from_closure (for owned
  closures retained by JS) or Function::closure_ref (for borrowed scoped
  closures). Pairs with the existing js_sys::WeakRef bindings.
  #5140

• Added support for well-known symbols in js_name, getter, and
  setter via the explicit bracket-string form
  "[Symbol.<name>]". This works for imported and exported methods,
  fields, getters, and setters. For example,
  #[wasm_bindgen(js_name = "[Symbol.iterator]")] on an exported method
  generates [Symbol.iterator]() { ... } on the generated JS class, and
  the same syntax works for getter / setter and for imported items.
  #4230

• Added level 2 bindings for ViewTransition to web-sys.
  #5138

• Add support for dynamic unions: a #[wasm_bindgen] enum that mixes string-literal
  variants with single-field tuple variants is now exported as an untagged TypeScript
  union and dispatched dynamically at the JS↔Rust boundary. The new enum-level
  #[wasm_bindgen(fallback)] attribute makes the last tuple variant an
  unconditional catch-all, supporting unions whose trailing variant has no
  runtime check (e.g., interface-only imports). String enums and dynamic
  unions now emit export type (was bare type) so the alias is a named
  export, and both honour the private flag to suppress the keyword.
  #4734
  #2153
  #2088

Fixed

• From<Promise<T>> for JsFuture<T> and IntoFuture for Promise<T> now
  accept any T: FromWasmAbi (rather than T: JsGeneric), letting
  imported async fns return dynamic-union enums.

• TryFromJsValue for C-style enums no longer accepts non-numeric values
  via JS unary + coercion. Previously calling dyn_into::<MyEnum>() on
  a string would silently coerce it via +"foo" (yielding NaN, then
  NaN as u32 = 0) and could match a discriminant by accident; the
  conversion now returns None for any value that is not a JS number.
  #4734

• Fix compilation failure with no_std + release
  #5134

• Raw identifiers (r#name) on enums, enum variants, extern types, statics,
  and impl blocks no longer leak the r# prefix into generated JS / TS
  output and shim names. The Rust-side identifier and the JS-side name are
  now tracked separately for enum variants, and all known identifier
  fallback paths apply Ident::unraw() so e.g.
  pub enum r#Enum { r#A } generates Enum.A instead of producing
  syntactically invalid JS.
  #4323

• Using the -C panic=unwind option when building for the bundler target
  would produce invalid JS.
  #5142

Changed

• js_sys::DataView now implements the js_sys::TypedArray trait. A
  FIXME notes that the trait should be renamed to ArrayBufferView in
  the next major release to better reflect the WebIDL spec name covering
  both DataView and the typed-array types.
  #5135

Added

• Added the slice_to_array attribute for imported JS functions, which makes a &[T] (or Option<&[T]>) argument arrive on the JS side as a plain Array rather than a typed array — without changing the Rust-side &[T] signature. Useful when binding JS APIs that take T[] rather than TypedArray<T>. For primitive element kinds the wire is the same zero-copy borrow used by plain &[T], with the JS-side shim wrapping the view in Array.from(...) to materialise the Array — no extra allocation. For String, JsValue, and JS-imported element types the Rust side builds a fresh [u32] index buffer that JS reads and frees, with per-element &T -> JsValue (refcount bump for handle-shaped types). No T: Clone bound is required. The attribute can be set per-fn (#[wasm_bindgen(slice_to_array)] fn ...) or per-block on an extern "C" { ... } declaration to apply to every imported function in that block. &[ExportedRustStruct] remains unsupported (use owned Vec<T> for that). Has no effect on exported functions; default &[T] (typed-array view / memory borrow) and owned Vec<T> semantics are unchanged for callers that didn't opt in. See the slice_to_array guide page. #5145

• Added js_sys::AggregateError bindings (constructor, errors getter, and new_with_message / new_with_options overloads). AggregateError represents multiple unrelated errors wrapped in a single error, e.g. as thrown by Promise.any when all input promises reject, along with js_sys::ErrorOptions, accepted by built-in error constructors. ErrorOptions::new(cause) constructs an instance pre-populated with cause, and get_cause / set_cause provide typed access to the property. All standard error constructors that previously took only a message (EvalError, RangeError, ReferenceError, SyntaxError, TypeError, URIError, WebAssembly.CompileError, WebAssembly.LinkError, WebAssembly.RuntimeError) now expose a new_with_options(message, &ErrorOptions) overload, and Error gains new_with_error_options(message, &ErrorOptions) alongside the existing untyped new_with_options. AggregateError::new_with_options also takes &ErrorOptions. #5139

• Added inheritance for Rust-exported types: an exported struct may declare #[wasm_bindgen(extends = Parent)] to inherit from another exported #[wasm_bindgen] struct. The macro injects a hidden parent: wasm_bindgen::Parent<Parent> field (a refcounted cell around the parent value) and emits class Child extends Parent in the generated JS / .d.ts. The child gets an AsRef<Parent<Parent>> impl for the direct parent, and threads per-class pointer slots through the wasm ABI so that instanceof Parent is true and parent methods dispatch soundly via the JS prototype chain. From inside child methods, parent data is reached via self.parent.borrow() / self.parent.borrow_mut(). See the new extends guide page. #5120

• Added js_sys::FinalizationRegistry bindings (constructor, register, register_with_token, and unregister). The cleanup callback parameter is typed as &Function<fn(JsValue) -> Undefined>, so closures created via Closure::new can be passed using Function::from_closure (for owned closures retained by JS) or Function::closure_ref (for borrowed scoped closures). Pairs with the existing js_sys::WeakRef bindings. #5140

• Added support for well-known symbols in js_name, getter, and setter via the explicit bracket-string form "[Symbol.<name>]". This works for imported and exported methods, fields, getters, and setters. For example, #[wasm_bindgen(js_name = "[Symbol.iterator]")] on an exported method generates [Symbol.iterator]() { ... } on the generated JS class, and the same syntax works for getter / setter and for imported items. #4230

• Added level 2 bindings for ViewTransition to web-sys. #5138

• Add support for dynamic unions: a #[wasm_bindgen] enum that mixes string-literal variants with single-field tuple variants is now exported as an untagged TypeScript union and dispatched dynamically at the JS↔Rust boundary. The new enum-level #[wasm_bindgen(fallback)] attribute makes the last tuple variant an unconditional catch-all, supporting unions whose trailing variant has no runtime check (e.g., interface-only imports). String enums and dynamic unions now emit export type (was bare type) so the alias is a named export, and both honour the private flag to suppress the keyword. #4734 #2153 #2088

Fixed

• From<Promise<T>> for JsFuture<T> and IntoFuture for Promise<T> now accept any T: FromWasmAbi (rather than T: JsGeneric), letting imported async fns return dynamic-union enums.

• TryFromJsValue for C-style enums no longer accepts non-numeric values via JS unary + coercion. Previously calling dyn_into::<MyEnum>() on a string would silently coerce it via +"foo" (yielding NaN, then NaN as u32 = 0) and could match a discriminant by accident; the conversion now returns None for any value that is not a JS number. #4734

• Fix compilation failure with no_std + release #5134

• Raw identifiers (r#name) on enums, enum variants, extern types, statics, and impl blocks no longer leak the r# prefix into generated JS / TS output and shim names. The Rust-side identifier and the JS-side name are now tracked separately for enum variants, and all known identifier fallback paths apply Ident::unraw() so e.g. pub enum r#Enum { r#A } generates Enum.A instead of producing syntactically invalid JS. #4323

• Using the -C panic=unwind option when building for the bundler target would produce invalid JS. #5142

Changed

• js_sys::DataView now implements the js_sys::TypedArray trait. A FIXME notes that the trait should be renamed to ArrayBufferView in the next major release to better reflect the WebIDL spec name covering both DataView and the typed-array types. #5135

0.2.121

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Added

• Added support for the wasm64-unknown-unknown target (memory64 / wasm64).
  usize / isize and raw pointers are now lowered through an f64 JS
  number ABI on wasm64 (matching the existing convention used for Option<u32>
  etc. on wasm32), with the CLI inspecting the module's memory type to pick
  the right codegen path. Includes a dedicated wasm64 CI job and test
  suite covering the new ABI paths.
  #5004

• Promise ergonomics: Promise::all_tuple and Promise::all_settled_tuple
  for heterogeneous concurrent awaits (arity 1..=8, destructure via
  .into_tuple()), and a new wasm_bindgen::IntoJsGeneric trait underpinning
  typed-Array inference (with codegen-emitted identity impls and a
  #[wasm_bindgen(no_into_js_generic)] opt-out for types like JsClosure).
  Also re-exports JsGeneric from the prelude. Typed collection on
  js_sys::Array<T> is exposed as the inherent constructor
  Array::<T>::from_iter_typed (and companion extend_typed), inferring T
  from the iterator item via IntoJsGeneric. The stable FromIterator /
  Extend impls on Array (= Array<JsValue>) bound by AsRef<JsValue>
  are preserved, so existing .collect::<Array>() call sites keep compiling
  unchanged. Fixes #5042.
  #5121,
  #5125

• Added wasm_bindgen::instance() to return the current
  WebAssembly.Instance. The generated JS glue retains the
  instantiated WebAssembly.Instance.
  #5118

• Added a --cfg=wasm_bindgen_use_js_sys opt-in that makes async macro codegen
  use js_sys::futures instead of wasm_bindgen_futures, dropping the need
  for wasm-bindgen-futures when the crate already depends on js-sys. A cfg
  is used rather than a Cargo feature so the choice stays scoped to the crate
  that opts in.
  #5112
  #5127

Changed

• Simplified generated web-sys bindings by omitting redundant
  #[wasm_bindgen] attributes when they match wasm-bindgen defaults, including
  structural method annotations and matching js_name entries. The
  #[wasm_bindgen] attribute parser now also accepts string-literal forms for
  extends, static_method_of, and vendor_prefix (alongside the existing
  bare-path/ident syntax), and the generator emits these arguments along with
  js_name as string literals so rustfmt can format the generated
  #[wasm_bindgen(...)] attributes uniformly.
  #5122

Fixed

• Fixed namespaced export identifiers in generated JS/TS to use qualified names
  consistently, resolving order-dependent codegen issues across platforms. Also
  fixed Vec<T> types in TS signatures to resolve through the identifier map.
  #5106

• Fixed wasm-bindgen-test-runner treating ChromeDriver stderr warnings as
  startup failures on macOS, causing a restart loop until timeout. The runner
  no longer uses stderr output to determine if a driver has failed; instead a
  per-attempt timeout detects stuck drivers and retries on a new port.
  #5111

0.2.120

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Added

• Added Error::stack_trace_limit() and Error::set_stack_trace_limit() bindings
  to js-sys for the non-standard V8 Error.stackTraceLimit property.
  #5082

• Added support for multiple #[wasm_bindgen(start)] functions, which are
  chained together at initialization, as well as a new
  #[wasm_bindgen(start, private)] to register a start function without
  exporting it as a public export.
  #5081

• Reinitialization is no longer automatically applied when using panic=unwind
  and --experimental-reset-state-function, instead it is triggered by any
  use of the handler::schedule_reinit() function under panic=unwind,
  which is supported from within the on_abort handler for reinit workflows.
  Renamed handler::reinit() to handler::schedule_reinit() and removed
  the set_on_reinit() handler. The __instance_terminated address
  is now always a simple boolean (0 = live, 1 = terminated).
  #5083

• handler::schedule_reinit() now works under panic=abort builds. Previously
  it was a no-op; it now sets the JS-side reinit flag and the next export call
  transparently creates a fresh WebAssembly.Instance.
  #5099

Changed

• MSRV bump from 1.71 to 1.76 for the CLI, and 1.82 to 1.86 for the API
  #5102

Fixed

• ES module import statements are now hoisted to the top of generated JS
  files, placed right after the @ts-self-types directive. This ensures
  valid ES module output since import declarations must precede other
  statements.
  #5103

• Fixed two CLI issues affecting WASM modules built by rustc 1.94+. First,
  a panic (failed to find N in function table) caused by lld emitting element
  segment offsets as global.get $__table_base or extended const expressions
  instead of plain i32.const N for large function tables; the fix adds a
  const-expression evaluator in get_function_table_entry and guards against
  integer underflow in multi-segment tables. Second, the descriptor interpreter
  now routes all global reads/writes through a single globals HashMap seeded
  from the module's own globals, and mirrors the module's actual linear memory
  rather than a fixed 32KB buffer, so the stack pointer's real value is valid
  without any override. This fixes panics like failed to find 32752 in function table caused by GOT.func.internal.* globals being misidentified as the
  stack pointer.
  #5076
  #5080
  #5093
  #5095

Added

• Added Error::stack_trace_limit() and Error::set_stack_trace_limit() bindings to js-sys for the non-standard V8 Error.stackTraceLimit property. #5082

• Added support for multiple #[wasm_bindgen(start)] functions, which are chained together at initialization, as well as a new #[wasm_bindgen(start, private)] to register a start function without exporting it as a public export. #5081

• Reinitialization is no longer automatically applied when using panic=unwind and --experimental-reset-state-function, instead it is triggered by any use of the handler::schedule_reinit() function under panic=unwind, which is supported from within the on_abort handler for reinit workflows. Renamed handler::reinit() to handler::schedule_reinit() and removed the set_on_reinit() handler. The __instance_terminated address is now always a simple boolean (0 = live, 1 = terminated). #5083

• handler::schedule_reinit() now works under panic=abort builds. Previously it was a no-op; it now sets the JS-side reinit flag and the next export call transparently creates a fresh WebAssembly.Instance. #5099

Changed

• MSRV bump from 1.71 to 1.76 for the CLI, and 1.82 to 1.86 for the API #5102

Fixed

• ES module import statements are now hoisted to the top of generated JS files, placed right after the @ts-self-types directive. This ensures valid ES module output since import declarations must precede other statements. #5103

• Fixed two CLI issues affecting WASM modules built by rustc 1.94+. First, a panic (failed to find N in function table) caused by lld emitting element segment offsets as global.get $__table_base or extended const expressions instead of plain i32.const N for large function tables; the fix adds a const-expression evaluator in get_function_table_entry and guards against integer underflow in multi-segment tables. Second, the descriptor interpreter now routes all global reads/writes through a single globals HashMap seeded from the module's own globals, and mirrors the module's actual linear memory rather than a fixed 32KB buffer, so the stack pointer's real value is valid without any override. This fixes panics like failed to find 32752 in function table caused by GOT.func.internal.* globals being misidentified as the stack pointer. #5076 #5080 #5093 #5095

0.2.118

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Fixed

• Fixed a regression introduced in #5026 where stable web-sys methods that
  accept a union type containing a [WbgGeneric] interface (e.g.
  ImageBitmapSource, which includes VideoFrame) incorrectly applied typed
  generics to all union expansions rather than only those whose argument type
  is itself [WbgGeneric]. In practice this caused Window::create_image_bitmap_with_*
  and the corresponding WorkerGlobalScope overloads to return
  Promise<ImageBitmap> instead of Promise<JsValue> for the stable
  (non-VideoFrame) call sites, breaking JsFuture::from(promise).await?.
  #5064
  #5073

Fixed

• Fixed a regression introduced in #5026 where stable web-sys methods that accept a union type containing a [WbgGeneric] interface (e.g. ImageBitmapSource, which includes VideoFrame) incorrectly applied typed generics to all union expansions rather than only those whose argument type is itself [WbgGeneric]. In practice this caused Window::create_image_bitmap_with_* and the corresponding WorkerGlobalScope overloads to return Promise<ImageBitmap> instead of Promise<JsValue> for the stable (non-VideoFrame) call sites, breaking JsFuture::from(promise).await?. #5064 #5073

• Fixed handling logic for environment variable WASM_BINDGEN_TEST_ADDRESS in the test runner, when running tests in headless mode. #5087

0.2.117

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Added

• Added js_sys::Float16Array bindings, DataView float16 accessors using f32, and raw [u16] helper APIs for interoperability with binary16 representations such as half::f16. #5033

Changed

• Updated to Walrus 0.26.1 for deterministic type section ordering. #5069

• The #[wasm_bindgen] macro now emits &mut (impl FnMut(...) + MaybeUnwindSafe) / &(impl Fn(...) + MaybeUnwindSafe) for raw &mut dyn FnMut / &dyn Fn import arguments instead of a hidden generic parameter and where-clause. The generated signature is cleaner and the MaybeUnwindSafe bound is visible directly in the argument position. The ABI and wire format are unchanged. When building with panic=unwind, closures that capture non-UnwindSafe values (e.g. &mut T, Cell<T>) must wrap them in AssertUnwindSafe before capture; on all other targets MaybeUnwindSafe is a no-op blanket impl. #5056

0.2.116

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Added

• console.debug/log/info/warn/error output from user-spawned Worker and SharedWorker instances is now forwarded to the CLI test runner during headless browser tests, just like output from the main thread. Works for blob URL workers, module workers, URL-based workers (importScripts), nested workers, and shared workers (including logs emitted before the first port connection). Non-cloneable arguments are serialized via String() rather than crashing the worker. The --nocapture flag is respected. #5037

• js_sys::Promise<T> now implements IntoFuture, enabling direct .await on any JS promise without a wrapper type. The wasm-bindgen-futures implementation has been moved into js-sys behind an optional futures feature, which is activated automatically when wasm-bindgen-futures is a dependency. All existing wasm_bindgen_futures::* import paths continue to work unchanged via re-exports. js_sys::futures is also available directly for users who want promise.await without depending on wasm-bindgen-futures. #5049

• Added --target emscripten support, generating a library_bindgen.js file for consumption by Emscripten at link time. Includes support for futures, JS closures, and TypeScript output. A new Emscripten-specific test runner is also included, along with CI integration. #4443

• Added VideoFrame, VideoColorSpace, and related WebCodecs dictionaries/enums to web-sys. #5008

• Added wasm_bindgen::handler module with set_on_abort and set_on_reinit hooks for panic=unwind builds. set_on_abort registers a callback invoked after the instance is terminated (hard abort, OOM, stack overflow). set_on_reinit registers a callback invoked after reinit() resets the WebAssembly instance via --experimental-reset-state-function. Handlers are stored as Wasm indirect-function-table indices so dispatch is safe even when linear memory is corrupt.

Changed

• Replaced per-closure generic destructors with a single __wbindgen_destroy_closure export. #5019

• Refactored the headless browser test runner logging pipeline for dramatically improved performance (>400x faster on Chrome, >10x on Firefox, ~5x on Safari). Switched to incremental DOM scraping with textContent.slice(offset), append-only output semantics, unified log capture across all log levels on failure, and browser-specific invisible-div optimizations (display:none for Chrome/Firefox, visibility:hidden for Safari). #4960

• TTY-gated status/clear output in the test runner shell to avoid \r control-character artifacts in non-interactive (CI) environments. #4960

• Added bench_console_log_10mb benchmark alongside the existing 1MB benchmark for the headless test runner. The main branch cannot complete this benchmark at any volume. #4960

• Updated to Walrus 0.26 #5057

Fixed

• Fixed argument order when calling multi-parameter functions in the wasm-bindgen interpreter by reversing the args collected from the stack. #5047

• Added support for per-operation [WbgGeneric] in WebIDL, restoring typed generic return types (e.g. Promise<ImageBitmap>) for createImageBitmap on Window and WorkerGlobalScope that were lost after the VideoFrame stabilization. #5026

• Fixed missing #[cfg(feature = "...")] gates on deprecated dictionary builder methods and getters for union-typed fields (e.g. {Open,Save,Directory}FilePickerOptions::start_in()), and fixed per-setter doc requirements to list each setter's own required features. #5039

• Fixed JsOption::new() to use undefined instead of null, to be compatible with Option::None and JS default parameters. #5023

• Fixed unsound unsafe transmutes in JsOption<T>::wrap, as_option, and into_option by replacing transmute_copy with unchecked_into(). Also tightened the JsGeneric trait bound and JsOption<T> impl block to require T: JsGeneric (which implies JsCast), preventing use with arbitrary non-JS types. #5030

• Fixed headless test runner emitting \r carriage-return sequences in non-TTY environments, which polluted captured logs in CI and complicated output-matching tests. #4960

• Fixed headless test runner printing incomplete and out-of-order log output on test failures by merging all five log levels into a single unified output div. #4960

• Fixed large test outputs (10MB+) causing oversized WebDriver responses that were either extremely slow or crashed completely, by switching to incremental streaming output collection. #4960

• Fixed a duplciate wasm export in node ESM atomics, when compiled in debug mode #5028

• Fixed a type inference regression (E0283: type annotations needed) introduced in v0.2.109 where the stable FromIterator and Extend impls on js_sys::Array were changed from A: AsRef<JsValue> to A: AsRef<T>. Because #[wasm_bindgen] generates multiple AsRef impls per type, the compiler could not uniquely resolve T, breaking code like Array::from_iter([my_wasm_value]) without explicit annotations. The stable impls are restored to A: AsRef<JsValue> (returning Array<JsValue>); the generic A: AsRef<T> forms remain available under js_sys_unstable_apis. #5052

• Fixed skip_typescript not being respected when using reexport, causing TypeScript definitions to be incorrectly emitted for re-exported items marked with #[wasm_bindgen(skip_typescript)]. #5051

Removed

Added

• Added [WbgGeneric] WebIDL extended attribute for opting stable dictionary and interface definitions into typed generics (the same signatures unstable APIs use), avoiding legacy &JsValue fallbacks. Applied to all new VideoFrame-related types. #5008

• Added unchecked_optional_param_type attribute for marking exported function parameters as optional in TypeScript (?:) and JSDoc ([paramName]) output. Mutually exclusive with unchecked_param_type. Required parameters after optional parameters are rejected at compile time. #5002

• Added termination detection for panic=unwind builds. When a non-JS exception (e.g. a Rust panic) escapes from Wasm, the instance is marked as terminated and subsequent calls from JS into Wasm will throw a Module terminated error instead of re-entering corrupted state. #5005

• When --reset-state is combined with panic=unwind builds, the Wasm instance is automatically reset after a fatal termination, allowing subsequent calls to succeed instead of throwing a Module terminated error. #5013

Changed

• Replaced runtime 0x80000000 vtable bit-flag for closure unwind safety with a compile-time const UNWIND_SAFE: bool generic on the invoke shim, OwnedClosure, and BorrowedClosure. Removes OwnedClosureUnwind and deduplicates internal closure helpers. The public API is unchanged. #5003

• Removed unused IntoWasmClosureRef*::WithLifetime types, WasmClosure::to_wasm_slice, and a lifetime from IntoWasmClosureRef*; moved Static associated type into WasmClosure. #5003

Fixed

• Fixed exported structs/enums/functions with the same js_name but different js_namespace values producing symbol collisions at compile time, by deriving internal wasm symbols from a qualified name that includes the namespace. #4977

• Fixed soundness hole in ScopedClosure's UpcastFrom that allowed to extend the lifetime after the original ScopedClosure was dropped. #5006

Changed

• Reduced usage of unsafe code: replaced transmute/transmute_copy with safe alternatives for Boolean/Null/Undefined constants and ArrayTuple conversions, unified duplicated AsRef/From impls for generic imported types, and removed the __wbindgen_object_is_undefined intrinsic in favor of a safe Rust-side equivalent. #4993

• Renamed __wbindgen_object_is_null_or_undefined intrinsic to __wbindgen_is_null_or_undefined and removed the __wbindgen_object_is_undefined intrinsic, replacing it with a safe Rust-side check. The is_null_or_undefined check now uses safe &JsValue ABI instead of raw u32. #4994

Fixed

• Fixed incorrect method naming for stable web-sys methods that reference unstable types (e.g. texImage2D taking a VideoFrame parameter). These methods were being named in a separate unstable expansion namespace, producing overly-short names like tex_image_2d instead of the correct tex_image_2d_with_u32_and_u32_and_video_frame. The fix separates the signature classification to distinguish "from unstable IDL" (authoritative overrides) from "stable method using an unstable type", ensuring the latter is named as part of the stable expansion. #4991

Removed

• Removed ImmediateClosure type introduced in 0.2.109. Stack-borrowed &dyn Fn / &mut dyn FnMut closures are now treated as unwind safe by default (panics are caught and converted to JS exceptions with proper unwinding). A unified ScopedClosure::immediate approach may be revisited in a future release. #4986

Fixed

• Restored backwards compatibility for breaking changes introduced in 0.2.110: re-added deprecated Promise::then2 binding, reverted Promise::all_settled stable signature to take &JsValue instead of owned Object, and added default type parameters (= JsValue) to ArrayIntoIter, ArrayIter, and Iter structs. #4979

Changed

• Refactor new closure methods - ensures that all closure constructor functions have the variants Closure::foo(), Closure::foo_aborting() and Closure::foo_assert_unwind_safe() this then fully allows switching from the UnwindSafe bound now being applies on foo() to use one of the alternatives, given these limitations of AssertUnwindSafe. The same applies to ImmediateClosure. In addition, mutable reentrancy guards are added for ImmediateClosure, and it is updated to be pass-by-value as well. #4975

Fixed

• Fixed a regression where Array.of1,... variants using generic Array<T> broke inference. Reverted to use non-generic JsValue arguments. In addition extends generic class hoisting to for constructors to also include static_method_of methods returning the own type, to allow Array::of generic to now be on the Array<T> impl block. #4974

Added

• Added support for erasable generic type parameters on imported JavaScript types, using sound type erasure in JS bindgen boundary. Includes updated js-sys bindings with generic implementations for many standard JS types and functions including Array<T>, Promise<T>, Map<K, V>, Iterator<T>, and more. #4876

• Added ScopedClosure<'a, T> as a unified closure type with lifetime parameter. ScopedClosure::borrow(&f) (for immutable Fn) and ScopedClosure::borrow_mut(&mut f) (for mutable FnMut) create borrowed closures that can capture non-'static references, ideal for immediate/synchronous JS callbacks. Closure<T> is now a type alias for ScopedClosure<'static, T>, maintaining backwards compatibility. Also added IntoWasmAbi implementation for Closure<T> enabling pass-by-value ownership transfer to JavaScript.

• Added ImmediateClosure<'a, T> as a lightweight, unwind-safe replacement for &dyn FnMut in immediate/synchronous callbacks. Unlike ScopedClosure, it has no JS call on creation, no JS call on drop, and no GC overhead—the same ABI as &dyn FnMut but with panic safety. Use ImmediateClosure::new(&f) for immutable Fn closures (easier to satisfy unwind safety) or ImmediateClosure::new_mut(&mut f) for mutable FnMut closures. Closure parameter types are automatically inferred from context. Also implements From<&ImmediateClosure<T>> for ScopedClosure<T> for API migration. #4950

• Implement #[wasm_bindgen(catch)] exception handling directly in Wasm using WebAssembly.JSTag when Wasm exception handling is available. This generates smaller and faster code by avoiding JavaScript handleError wrapper functions. #4942

• Add Node.js worker_threads support for atomics builds. When targeting Node.js with atomics enabled, wasm-bindgen now generates initSync({ module, memory, thread_stack_size }) and __wbg_get_imports(memory) functions that allow worker threads to initialize with a shared WebAssembly.Memory and pre-compiled module. Auto-initialization occurs only on the main thread for backwards compatibility.

• Added a panic message when a getter has more than one argument. #4936

• Added support for WebIDL namespace attributes in wasm-bindgen-webidl. This enables APIs like the CSS Custom Highlight API which adds the highlights attribute to the CSS namespace. #4930

• Added stable ShowPopoverOptions dictionary and show_popover_with_options() method to HtmlElement, and unstable TogglePopoverOptions dictionary per the WHATWG HTML spec. #4968

• Added unstable Geolocation API types per the latest W3C spec: GeolocationCoordinates, GeolocationPosition, and GeolocationPositionError. The Geolocation interface now has both stable methods (using the old Position/PositionError types with [Throws]) and unstable methods (using the new types without [Throws]}, matching actual browser behavior). #2578

• Added matrixTransform() method to DOMPointReadOnly in web-sys. #4962

• Added the web and node targets to the --experimental-reset-state-function flag. #4909

• Added oncancel event handler to GlobalEventHandlers (available on HtmlElement, Document, Window, etc.). #4542

• Added CommandEvent and CommandEventInit from the Invoker Commands API. #4552

• Added AbstractRange, StaticRange, and StaticRangeInit interfaces. #4221

• Updated WebCodecs API to Working Draft 2026-01-29 and MediaRecorder API to 2025-04-17. Added rotation and flip to VideoDecoderConfig. #4411

• Added support for unstable WebIDL to override stable attribute types, allowing corrected type signatures behind web_sys_unstable_apis. Applied to MouseEvent coordinate attributes (clientX, clientY, screenX, screenY, offsetX, offsetY, pageX, pageY) which now return f64 instead of i32 when unstable APIs are enabled, per the CSSOM View spec draft. #4935

• Added support for unstable WebIDL to override stable method return types. This enables User Timing Level 3 APIs where Performance.mark() and Performance.measure() return PerformanceMark and PerformanceMeasure respectively (instead of undefined) when web_sys_unstable_apis is enabled. Also added PerformanceMarkOptions, PerformanceMeasureOptions, and the detail attribute on marks/measures. #3734

• Added non-standard mode option for FileSystemFileHandle.createSyncAccessHandle(). Also improved WebIDL generator to track stability at the signature level, allowing stable methods to have unstable overloads. #4928

• Updated WebGPU bindings to the February 2026 spec. Dictionary fields with union types now generate multiple type-safe setters (e.g. set_resource_gpu_sampler(), set_resource_gpu_texture_view()) alongside a deprecated fallback setter. Sequence arguments in unstable APIs now use typed slices (&[T]) instead of &JsValue. Fixed inner string enum types to use JsString in generic positions, added BigInt to builtin identifiers, and fixed dictionary field feature gates to not over-constrain getters with setter type requirements. #4955

• Improved dictionary union type expansion: stable fallback setters are no longer deprecated, and unstable builder methods now use the first typed variant instead of &JsValue. Dictionaries with required union fields now generate expanded constructors for each variant (e.g. new(), new_with_gpu_texture_view()), with duplicate-signature variants elided. #4966

Changed

• Increased externref stack size from 128 to 1024 slots to prevent "table index is out of bounds" errors in applications with deep call stacks or many concurrent async operations. #4951

• Closure::new(), Closure::once(), and related methods now require UnwindSafe bounds on closures when building with panic=unwind. New _aborting variants (new_aborting(), once_aborting(), etc.) are provided for closures that don't need panic catching and want to avoid the UnwindSafe requirement. #4893

• global does not use the unsafe-eval new Function trick anymore allowing to have CSP strict compliant packages with wasm-bindgen. #4910

• eval and Function constructors are now gated behind the unsafe-eval feature. #4914

Fixed

• Fixed incorrect JS export names when LLVM merges identical functions at opt-level >= 2. #4946

• Fixed incorrect Closure adapter deduplication when wasm-ld's Identical Code Folding merges invoke functions for different closure types into the same export. #4953

• Fixed ReferenceError when using Rust struct names that conflict with JS builtins (e.g., Array). The constructor now correctly uses the aliased FinalizationRegistry identifier. #4932

• Fixed Element::scroll_top(), Element::scroll_left(), and HtmlElement::scroll_top() to return f64 instead of i32 per the CSSOM View spec, behind web_sys_unstable_apis. The stable API is unchanged for backwards compatibility. #4525

• Added spec-compliant i32 parameter types for CanvasRenderingContext2d::get_image_data() and put_image_data() (and OffscreenCanvasRenderingContext2d equivalents) behind web_sys_unstable_apis. Per the HTML spec, getImageData and putImageData use long (i32) for coordinates, not double (f64). The stable API is unchanged for backwards compatibility. #1920

• Fixed incorrect #[cfg(web_sys_unstable_apis)] gating on stable method signatures that share a WebIDL operation with unstable overloads. For example, Clipboard.read() (0 args) was incorrectly gated as unstable because the unstable read(options) overload existed. The WebIDL code generator now uses an authoritative expansion model where stable and unstable signature sets are built independently and compared: identical signatures merge (no gate), stable-only signatures get not(unstable), and unstable-only signatures get unstable. Also adds typed generics (Promise<T>, Array<T>, Function<fn(...)>, etc.) to all unstable API methods, and adds missing PhotoCapabilities, PhotoSettings, MediaSettingsRange, Point2D, RedEyeReduction, FillLightMode, and MeteringMode types from the W3C Image Capture spec. #4964

• Fixed unfulfilled_lint_expectations warnings when using #[expect(...)] attributes on functions annotated with #[wasm_bindgen]. The #[expect] attributes are now converted to #[allow] in generated code to prevent spurious warnings. #4409

Fixed

• Fixed regression where panic=unwind builds for non-Wasm targets would trigger UnwindSafe assertions. #4903

Added

• Support catching panics, and raising JS Exceptions for them, when building with panic=unwind on nightly, with the std feature. #4790

• Added support for passing &[JsValue] slices from Rust to JavaScript functions. #4872

• Added private attribute on exported types to allow generating exports and structs as implicit internal exported types for function arguments and returns, without exporting them on the public interface. #4788

• Added iter_custom and iter_custom_future for bench to do custom measurements. #4841

• Added Window Management API. #4843

Changed

• Changed WASM import namespace from wbg to ./{name}_bg.js for web and no-modules targets, aligning with bundler and experimental-nodejs-module to enable cross-target WASM sharing. #4850

• Replace WASM_BINDGEN_UNSTABLE_TEST_PROFRAW_OUT and WASM_BINDGEN_UNSTABLE_TEST_PROFRAW_PREFIX with parsing LLVM_PROFILE_FILE analogous to Rust test coverage. #4367

• Typescript custom sections sorted alphabetically across codegen-units. #4738

• Optimized demangling performance by removing redundant string formatting #4867

• Changed WASM import namespace from __wbindgen_placeholder__ to ./{name}_bg.js for node targets, aligning with bundler and experimental-nodejs-module to enable cross-target WASM sharing. #4869

• Changed WASM import namespace from __wbindgen_placeholder__ to ./{name}_bg.js for deno and module targets, aligning with node, bundler and experimental-nodejs-module to enable cross-target WASM sharing. #4871

• Consolidate JavaScript glue generation Move target-specific JS emission into a single finalize phase, reducing branching and making the generated output more consistent across targets.

  • Centralize JS output assembly in a single finalize phase (exports/imports/wasm loading).
  • Make --target experimental-nodejs-module emit one JS entrypoint (no separate _bg.js).
  • Ensure Node (CJS/ESM) and bundler entrypoints only expose public exports (no internal import shims).
  • Add /* @ts-self-types="./<name>.d.ts" */ to JS entrypoints for JSR/Deno resolution.
  • Refresh reference test fixtures. #4879

• Forward worker errors to test output in the test runner. #4855

Fixed

• Fix: Include doc comments in TypeScript definitions for classes #4858

• Interpreter: support try_table blocks #4862

• Interpreter: Stop interpretting descriptor after __wbindgen_describe_cast #4862