WebExtensions

 WebExtensions  are a cross-browser way to develop browser add-ons. The Browser Extension Community Group works on the Browser Extensions standard.

Browser Documentation
As there isn’t a single resource or standard (yet), different browsers publish separate documentation. Even though there is much overlap. MDN publishes an overview of browser support of the separate APIs.


 * Google Chrome: Extensions
 * Microsoft Edge: Microsoft Edge extensions
 * Mozilla Firefox: Browser Extensions
 * Opera: Extensions Documentation
 * Safari: Safari Web Extensions

IndieWeb Examples

 * Omnibear: a Micropub client in your browser.