Polyfill Fastly

Fastly Polyfill is a web compatibility service that helps websites support browser features across different environments. It accepts a request describing the features a site needs and returns a bundle containing only the polyfills required by the requesting browser. This targeted approach is designed to avoid sending unnecessary code, while making modern web capabilities available to browsers that do not support them natively.

The service provides the Polyfill Library, with multiple versions available, and a browser-based bundle builder for configuring output. Users can select individual polyfills or feature sets, including collections for standards such as ES5, ES2015, and later editions, as well as browser and DOM APIs. Options also include filtering the available polyfills and specifying a callback. The generated bundle can be referenced through a JavaScript URL for use in a website. Fastly Polyfill presents its purpose as helping users “upgrade the web” automatically, with polyfills covering areas such as arrays, promises, strings, document elements, and browser interfaces. Its site also provides terms and privacy information.