The Mozilla Foundation has made Firefox 58 files available for download on its
official FTP servers. An official
announcement will be made later today when the organization will also release the final changelog.
Firefox 58 marks the first major release since mid-November last year, when Mozilla released Firefox 57, a version that overhauled large parts of the Firefox codebase, including its old add-on system, with Mozilla choosing a new system based on the Chromium-compatible and standardized WebExtensions API.
Work has continued on improving Firefox performance
These changes have continued two months later, in today's Firefox 58 release. Except for a few changes to Firefox's settings panel, most of the new Firefox features are under the browser's hood.
For example, Firefox 58 comes with a new feature called
Off-Main-Thread painting, which are improvements to Firefox's built-in graphics engine.
There is also a new system called the
JavaScript Startup Bytecode Cache (JSBC) for improving the browser startup time, and the integration of
WebRender, a new web-rendering engine initially developed for Mozilla Servo testbed browser, and which has now been integrated into Firefox. Other under-the-hood feature improvements are detailed
here.