# What changed in simplejson

> 9 changes in simplejson 4 from its official release notes, upgrade guides and advisories: 1 breaking, 1 new APIs and options. Each one cited. Sources checked 2026-10-25. HTML: https://unstale.sh/pypi/simplejson/

To see which of these apply to a repository, run `npx @unstale/cli init` in it.

## simplejson 4

### Breaking changes

- Circular references introduced by custom JSON methods are now checked. (4.2.0) — [release notes](https://github.com/simplejson/simplejson/releases/tag/v4.2.0)

### New APIs and options

- Large integer stringification thresholds are supported in both encoders. (4.2.0) — [release notes](https://github.com/simplejson/simplejson/releases/tag/v4.2.0)

### Tooling

- Wheels are now built for CPython 3.15, making them available to developers using that Python version. (4.2.0) — [release notes](https://github.com/simplejson/simplejson/releases/tag/v4.2.0)
- Wheel builds are now available for Python 2.7 on Windows platforms. (4.1.1) — [release notes](https://github.com/simplejson/simplejson/releases/tag/v4.1.1)

### Fixes and other changes

- The C scanner now uses the first-key error message. (4.2.0) — [release notes](https://github.com/simplejson/simplejson/releases/tag/v4.2.0)
- The reported position for a control character is corrected when content precedes it. (4.1.2) — [release notes](https://github.com/simplejson/simplejson/releases/tag/v4.1.2)
- Invalid \X escape errors report the offending character rather than the backslash. (4.1.2) — [release notes](https://github.com/simplejson/simplejson/releases/tag/v4.1.2)
- The encoder handles non-finite Decimals the same way it handles floats. (4.1.2) — [release notes](https://github.com/simplejson/simplejson/releases/tag/v4.1.2)
- Illegal trailing comma errors report the comma position. (4.1.2) — [release notes](https://github.com/simplejson/simplejson/releases/tag/v4.1.2)