Check this setting: Firefox 57 uses multi-cores Firefox Web Browser - Offline Installation file . . . https://www.mozilla.org/en-US/firefox/all/?q=english Tools / Options / General / Performance [check] Use recommended performance settings (default) Firefox's performance settings . . . https://support.mozilla.org/en-US/kb/performance-settings?as=u&utm_source=inproduct Tip: If your computer's system information shows more than 8 GB of RAM, you might want to try bumping up the number of content processes that Firefox uses from its default value. Additional content processes can improve performance when using multiple tabs, but will also use more memory. . . . Content process limit = 4 (default) . . . 11/16/17 I have 16 GB RAM, try it on the Max of 7 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Entering the Quantum Era—How Firefox got fast again and where it’s going to get faster – Mozilla Hacks – the Web developer blog . . . Released 11/14/17 . . . https://hacks.mozilla.org/2017/11/entering-the-quantum-era-how-firefox-got-fast-again-and-where-its-going-to-get-faster/ Coarse-grained parallelism makes better use of the hardware… but it doesn’t make the best use of it. When you split up these web pages across different cores, some of them don’t have work to do. So those cores will sit idle. At the same time, a new page being fired up on a new core takes just as long as it would if the CPU were single core. Splitting content windows across different cores It would be great to be able to use all of those cores to process the new page as it’s loading. Then you could get that work done faster. But with coarse-grained parallelism, you can’t split off any of the work from one core to the other cores. There are no boundaries between the work. With fine-grained parallelism, you break up this larger task into smaller units that can then be sent to different cores. For example, if you have something like the Pinterest website, you can split up the different pinned items and send those to be processed by different cores. This doesn’t just help with latency like the coarse-grained parallelism did. It also helps with pure speed. The page loads faster because the work is split up across all the cores. And as you add more cores, your page load keeps getting faster the more cores you add. So we saw that this was the future, but it wasn’t entirely clear how to get there. Because to make this fine-grained parallelism fast, you usually need to share memory between the cores. But that gives you those data races that I talked about before. But we knew that the browser had to make this shift, so we started investing in research. We created a language that was free of these data races—Rust. Then we created a browser engine— Servo — that made full use of this fine-grained parallelism. Through that, we proved that this could work and that you could actually have fewer bugs while going faster. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

What security software do you have? Did you make sure that your security software isn't blocking the current Firefox release? This is usually the first to check if you experience issues after updating, especially on Windows.