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NuGet · #24 most downloaded on NuGet
.NET models with JSON and YAML writers for OpenAPI specification
Last release 1 months ago
20 Aug 2026
Ships fairly regularly
a new release about every 2 weeks
Most releases are documented
notes for 42 of the last 60 stable releases
12 versions withdrawn
withdrawn after publishing
127 years old
149 releases · first in 1900
duplicate schema example when serializing to v2
marks deprecated properties from the specification as obsolete
One column per quarter.
adds support for anchor and id external resolution
add JsonConverter for OpenApiSchema System.Text.Json serialization
add contains/minContains/maxContains members
reader: remove ParseNode infrastructure
reader: preserve Null flag when nullable appears before type in V3.0/V3.1/V3.2 deserializers
library: handle circular schema references
null reference exception for boolean component schemas
hidi: update Microsoft.OpenApi.OData to 3.2.1
security scheme references serialization
library: add Extensions support for schema references in v3.1/v3.2; add SerializeAsV32 with loop detection
library: preserve PatternProperties as x-jsonschema-patternProperties extension for OpenAPI v2/v3.0 serialization
models: add shared Content interface
models: add shared Content interface
hidi validate command now logs warnings
### Bug Fixes * Support custom tag ordering (008576c) * Support custom tag ordering
correct error pointer when extension parser throws OpenApiException
schema: always serialize additionalProperties: false
load JSON documents that are preceded by multiple whitespace
additional properties serialization should not emit a schema in v2
empty strings should be quoted in yaml
> Note: Please refer to the upgrade guide for a detailed description of the breaking changes.
Note: Please refer to the upgrade guide for a detailed description of the breaking changes.
Note: ASP.net users should remain on version 1.X for ASP.net < 10, and version 2.X for ASP.net 10, this new major version will be implemented in a future version of ASP.net, more information
duplicate schema example when serializing to v2
2.12.1 (2026-08-19) Bug Fixes circular ref guard ( #3033 ) ( #3039 ) ( 406e6fd ) harden yaml parsing
marks deprecated properties from the specification as obsolete
adds support for anchor and id external resolution
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Nothing published for this version
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Nothing published for this version
Nothing published for this version
Nothing published for this version
Nothing published for this version
Nothing published for this version
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Nothing published for this version
wrap extension parser calls in try-catch to ensure correct error pointers
schema: always serialize additionalProperties: false
Add type: "null" downcasting when in oneOf and anyOf for OpenAPI v3
type: "null" downcasting when in oneOf and anyOf for OpenAPI v3 (782cf8d)load JSON documents that are preceded by multiple whitespace
additional properties serialization should not emit a schema in v2
empty strings should be quoted in yaml
a bug where null sentinel value would appear in YAML documents
an issue where numeric property names would be missing quotes in yaml conversion
adds a null value sentinel to enable roundtrip serializations of JsonNode typed properties
a bug where empty collections would not be serialized for default values
use settings for terse output in serialization extension methods
Improve server creation and URL handling logic to maintain port
typo in allowReserved property name for deserialization
Fix URL processing in InternalLoad method would not detect the filename/scheme properly in some scenarios
file access for "file" URI scheme with special characters
adds the detected format as part of the diagnostic
add Validation Rule for path operations to not have a request body
adds a default validation rule for unresolved references
add missing disposable for stream
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