Gecko (software)
free HTML layout engine
Gecko is a browser engine developed by Mozilla. It is used in the Firefox browser, the Thunderbird email client, and in a discontinued state on AOL's Netscape 6, Netscape 7, Netscape Browser and Netscape Navigator 9; this is alongside many other projects.
Gecko is designed to support open Internet standards, and is used by different applications to display web pages and, in some cases, an application's user interface itself (by rendering XUL). Gecko offers a rich programming API that makes it suitable for a wide variety of roles in Internet-enabled applications, such as web browsers, content presentation, and client/server.
Gecko is written in C++ and JavaScript, and, since 2016, additionally in Rust. It is free and open-source software subject to the terms of the Mozilla Public License version 2. Mozilla officially supports its use on Android, Linux, macOS, and Windows.
History
Development of the layout engine now known as Gecko began at Netscape in 1997, following the company's purchase of DigitalStyle. The existing Netscape rendering engine, originally written for Netscape Navigator 1.0 and upgraded through the years, was slow, did not comply well with W3C standards, had limited support for dynamic HTML and lacked features such as incremental reflow (when the layout engine rearranges elements on the screen as new data is downloaded and added to the page). The new layout engine was developed in parallel with the old, with the intention being to integrate it into Netscape Communicator when it was mature and stable.
“Gecko (software)” enters the record as free HTML layout engine. Crown Archives preserves that source wording while asking what Gecko, software and free can confirm, complicate or overturn.
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“Gecko (software)” is worth following because a concise public description often conceals a longer documentary argument. Here, Gecko, software and free provides the most credible route into that argument.
Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Sep 20, 2026. The linked authority identifier is Q487834. 1 of 7 selected statements include explicit references; 6 carry qualifiers and 1 use preferred rank. The first chronological checks are 2016 and 1997.
Overview language is designed for orientation and should not be treated as a substitute for the evidence cited beneath it. The lead is largely declarative, so disagreement and counter-evidence require a deliberate search beyond the opening account. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
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This entry incorporates text from “Gecko (software)” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.