As was previously announced, the Mozilla devs are working on an overhaul to Firefox's rendering engine. Instead of rendering the web on a CPU with GPU acceleration as a side feature, like Chrome, Firefox and Edge currently do, "Webrender" approaches the task more like a game engine would, and make heavy use of modern GPUs. Previously, the feature was only enabled on specific desktop Nvidia GPUs, meaning users had to force enable it in about:config on most platforms, But in Mozilla's latest graphics team newsletter, the Firefox developers say that Webrender is now enabled by default in Firefox Nightly on some Intel and AMD GPUs. Digging a little deeper, the revisions on Mozilla's website show that webrender is enabled on generation 9 Skylake (UHD 530) Intel IGPs and up, as well as AMD's "Sea Islands" GPUs (which includes the R9 290X, Kaveri APUs, and the 7790) and up. I've been using Firefox Nightly (with webrender force enabled) and Vivaldi (which is based on Chromium) side by side for the past couple of months, both on a desktop PC with a 980 TI and a laptop with an old AMD llano APU, and to my eyes, the experience is like night an day. Web pages consistently load significantly faster on Firefox, scrolling through them feels smoother and stutter-free (particularly on a high-refresh monitor), and aside from one funky update a few months ago, the experience has been just as stable as the Chromium-based browser. GPU usage also spikes higher when rendering webpages on the bleeding edge Firefox build. As soeren-hentzschel points out, Webrender is scheduled to come to the stable Firefox channel on May 14, 2019, but you can try running Webrender on Firefox Nightly right now. Unfortunately, there's no word on when the feature will make it to Android and iOS devices.