Browserslist

Browserslist is an open-source project and tool that defines which web browsers should be targeted when building front-end applications. It provides a simple query language and a shared data set that let different development tools make consistent decisions about transpilation, polyfills, and vendor prefixes.

The core idea is to specify browser coverage in one place so tools such as Autoprefixer, Babel (preset-env), and other CSS or JavaScript tooling can determine which features to enable or downlevel support for. Browserslist relies on data from caniuse-lite to map queries to actual browser versions and supports multiple environments and configurations.

Configuration can be done in several ways. The most common is a browserslist field in package.json, a separate .browserslistrc file, or a browserslist.config.js file. It supports environment-specific lists, typically labeled production and development, allowing different targets for builds intended for production versus local development. Queries are written in a human-friendly syntax, for example: "> 1%", "last 2 versions", "not dead". You can combine multiple queries and also include specific entries such as "Firefox ESR" or "Chrome 90" for precise targeting.

Usage and behavior: Tools that read Browserslist resolve the actual list of targeted browsers for the current environment. This resolution informs which JavaScript syntax to transpile, which polyfills to include, and which CSS prefixes to apply. The underlying data can be updated with commands provided by the tools, such as updating the caniuse data used by the project.

Scope and reception: Browserslist has become a de facto standard in the front-end ecosystem, widely adopted by major build and linting tools to ensure consistent and maintainable browser targets across projects.