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PyPI · #254 most downloaded on PyPI
Fastest Python implementation of JSON schema
Last release 1 months ago
15 Aug 2026
Release timing varies
gaps range from 3 weeks to 12 months
Nearly every release is documented
notes for 47 of 47 stable releases
1 version withdrawn
withdrawn after publishing
10 years old
48 releases · first in 2016
Fixed wrong results of anyOf, oneOf, not, if/then/else, contains and propertyNames when fast_fail is off
fast_fail is off$ref when fast_fail is offdependencies validation (prevents schema-controlled code injection)* Fixed min Python version
One column per quarter.
Fixed IPv4 validation (rejecting leading zeros)
fast_fail to False)* Fixed regexp for IPv6 format
Fixed ResourceWarning where file was not properly closed
Added detailed_exceptions flag (default to True to avoid breaking change) - when used, results are twice as fast
not is invaliddetailed_exceptions flag (default to True to avoid breaking change) - when used, results are twice as fastValidate more deeply required attribute
Validate more deeply required attribute
required must have unique itemsrequired items (item is required, but is not listed in properties)Fixed date format to accept only two digit months and days
Added use_formats parameter
Added use_formats parameter
Lazy import of urllib to improve import performance
Improved error message for required props - only missing are reported
* Fixed tests in sdist
* Added support for Decimals * Added tests in sdist
Fix variable name resolving with references
Fix compile to code tests to run them on any platform
Fix uniqueItems when explicitly set to False
Fix generating invalid code for some schemas using items
Readable regexps in generated code
Fix if-else block in anyOf block
Fix parsing date-time with +hhmm format
Fix additional property equal to empty object is the same as True
use_default to have option turn off default feature (True by default to be compatible)* Fix missing dependencies * Fix schema cache
Add extra properties to error message when additionalProperties are set to False
* Tuple is also valid array
Fix of additionalProperties=true for JSON schema 4
additionalProperties=true for JSON schema 4Fix of undefined format exception message
Optimization: do not do the same type checks, keep it in one block if possible
Updated JSON Schema test suites
Fix of properties (local variable referenced before assignment).
Fix of additionalProperties (colliding variable names).
Fix pattern regexps with a space.
Use of urllib instead of requests for smaller memory usage.
Fix quotes in enum generating invalid code
* Fix regexps for Python 3.7
Swap $ in regexps to \Z to follow ECMA 262 ($ matches really the end of the string, not the end or new line and the end). Because of that your regular
E-mail regex allows any e-mail with @
Fix overriding variables (in pattern properties, property names, unique items and contains)
* Fix regex of hostname
Fix code generation with long regex patterns
Fix code generation with regex patterns
* Support of draft-06 * Support of draft-07 * Code generation to a file
* Bugfixing
* Support of definitions * Support of referencies
* Better date-time regex * Support of dependencies
* Fix patter inside of anyOf
* Support of formats * Support of properties
* Support of float numbers
* First version
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