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A polyfill is a term coined by Remy Sharp for a snippet of code that adds support for a feature to browsers that don’t offer it natively.

They let you write code once and provide deeper backwards compatibility and browser support—without having to use a clunky preprocessor or command line tool.

How to use a polyfill

Drop the polyfill from the list below into your codebase, ideally before any code that uses the JavaScript method or browser API you’re polyfilling.

Alternatively, you can automatically polyfill your site with a service like

The Polyfills

Some were written by me. Others were squirreled away from around the web. Links to the source and attribution are included with each.