Gecko is Mozilla’s browser engine, the core software that Firefox uses to render web pages, execute browser features, and process many parts of web content. It is the technical layer between the site and the user interface, handling HTML, CSS, JavaScript integration, layout, and related browser components.
In cyber security, the engine matters because it defines much of the browser’s attack surface. Vulnerabilities in Gecko can be abused through malicious pages, weaponized scripts, or drive-by content that tries to crash, escape sandboxing, or execute code. Defenders care about Gecko because patching, isolation controls, and enterprise policies all depend on how the engine is built and updated. In managed environments, it is also relevant to logging, extension control, and safe browsing policy enforcement. Gecko gives organizations a non-Chromium browser base, which can support standardization and governance choices, but security still depends on fast updates and careful configuration.