# Compatibility

This file is the canonical resource for compatibility goals for the libraries that make up Sinon.JS.

## ES2017

Sinon has historically been written as [ES5][es5], but starting from Sinon 10 we made the breaking change to allow more modern ECMAScript versions, starting with ECMAScript [2017][es2017].
The source version is [ES2017][es2017] and requires no transpiler or polyfills in supporting runtimes.

For legacy runtimes, a transpiler can be used by dependent projects., but use of newer APIs might break. If you need to support older browsers, have a look at Sinon 9.

## Runtimes

Sinon.JS aims at supporting the following runtimes (from our shared [eslint-config][shared-config]).



```
> 0.5%
last 2 versions
Firefox ESR
not dead
not IE 11
not op_mini all
maintained node versions
```



The compatibility is enforced using [`eslint-plugin-compat`](https://www.npmjs.com/package/eslint-plugin-compat).

To see what that means in practice, you can use https://browserslist.dev

[es5]: http://www.ecma-international.org/ecma-262/5.1/
[es2017]: https://262.ecma-international.org/8.0/
[shared-config]: https://github.com/sinonjs/eslint-config
