Note: If you're familiar with the basic concepts of browser extensions, skip this section to see how extension files are put together. Then, use the reference documentation to start building your extension. Visit Firefox Extension Workshop to learn more about the workflow for testing, publishing, and extensions for Firefox.
This article walks through creating an extension for Firefox, from start to finish. The extension adds a red border to any pages loaded from "mozilla.org
" or any of its subdomains.
The source code for this example is on GitHub: https://github.com/mdn/webextensions-examples/tree/master/borderify.