Mozilla has recently released Firefox Preview to the Android Play store. It's a new iteration of the Firefox Mobile web browser that was built from scratch around GekcoView, an open-source web browsing component that is based on the Gecko browser engine.
Firefox Preview isn't meant to replace Firefox Mobile that is still available on the Android Play store. Instead, it was created to build, test and deliver unique features, and explore new concepts for how mobile browsers should look and feel. It also offers a broader testbed for GeckoView - as its usage has been limited to smaller projects so far (such as Firefox Focus, Reference Browser, and Firefox Reality).
But the GeckoView component that powers Firefox Preview isn't intended solely for internal Mozilla use. It is offered as an alternative to the Android built-in WebView, which is commonly used by web applications to display web pages within the context of their app. The GeckoView component offers several advanced web capabilities that are lacking in the native Android WebView component, which was never designed to enable the creation of a full "web browser" experience. However, these capabilities come with a price; adding the GeckoView component adds up to 30MB to your bundle size, which could be quite significant for smaller applications.
Using a standalone component for displaying web content comes with an additional benefit - it is not dependent on the operating system version, a problem that many developers struggle with. While Google is trying to tackle the problem by pushing towards automatic upgrades to the WebView component isn't much better, developers can still face situations where the WebView component they worked on is different than the one that is used by their customers.
At the moment, the GecKoView component is only available for Android, as Apple refuses to allow third-party web engines into their ecosystem. Sadly, this limits the usability of GeckoView for hybrid mobile developers who use Cordova or Capacitor, and who would benefit from using a single web engine across both operating systems. Mozilla and others have protested Apple's decision in the past, but it does not seem likely to change.
You can read more about Firefox Preview in the official Mozilla blog post.
GeckoView is released under the MPL (Mozilla Public License). Documentation can be found in their Github repository, though the code itself is managed in Mozilla Central.
