MDN Web Docs Glossary: Definitions of Web-related terms

Web technologies contain long lists of jargon and abbreviations that are used in documentation and coding. This glossary provides definitions of words and abbreviations you need to know to successfully understand and build for the web.

Glossary terms can be selected from the sidebar (or listed below on mobile devices).

Note: This glossary is a never-ending work in progress. You can help improve it by writing new entries or by making the existing ones better.

Note: If you'd prefer a web development glossary in book form, check out The Web Development Glossary (EPUB, MOBI, PDF). It’s a third-party glossary that includes the entries found here, and also adds a wide range of additional entries.

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Mozilla Firefox
Mozilla Firefox is a free open-source browser whose development is overseen by the Mozilla Corporation. Firefox runs on Windows, OS X, Linux, and Android.