# What changed in tomli

> 7 changes in tomli 1 to 2 from its official release notes, upgrade guides and advisories: 2 breaking. Each one cited. Sources checked 2026-10-27. HTML: https://unstale.sh/pypi/tomli/

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

## tomli 2

### Breaking changes

- Limits the number of parts in a TOML key to address quadratic time complexity. (2.4.1) — [release notes](https://github.com/hukkin/tomli/blob/5d51b8f567df7a0e93e6da889b70f507627e9892/CHANGELOG.md#241)

### Performance

- Limits the number of parts in a TOML key to address quadratic time complexity. (2.3.1) — [release notes](https://github.com/hukkin/tomli/blob/5d51b8f567df7a0e93e6da889b70f507627e9892/CHANGELOG.md#231)

### Behavior and default changes

- Added compatibility with TOML v1.1.0. (2.4.0) — [release notes](https://github.com/hukkin/tomli/blob/5d51b8f567df7a0e93e6da889b70f507627e9892/CHANGELOG.md#240)

### Tooling

- Added binary wheels for Windows arm64. (2.4.0) — [release notes](https://github.com/hukkin/tomli/blob/5d51b8f567df7a0e93e6da889b70f507627e9892/CHANGELOG.md#240)

### Fixes and other changes

- Binary wheels are now available for Python 3.15. (2.5.0) — [release notes](https://github.com/hukkin/tomli/blob/5d51b8f567df7a0e93e6da889b70f507627e9892/CHANGELOG.md#250)
- The limit is set to 400 to prevent mypyc-generated binaries from crashing unrecoverably in constrained environments. (2.3.2, 2.5.0) — [release notes](https://github.com/hukkin/tomli/blob/5d51b8f567df7a0e93e6da889b70f507627e9892/CHANGELOG.md#250), [release notes](https://github.com/hukkin/tomli/blob/5d51b8f567df7a0e93e6da889b70f507627e9892/CHANGELOG.md#232)

## tomli 1

### Breaking changes

- Overwriting implicitly in an inline table raises TOMLDecodeError instead of KeyError. (1.0.0) — [release notes](https://github.com/hukkin/tomli/blob/HEAD/CHANGELOG.md)