Tab warming is a fairly new concept to Firefox browser. It can be simply explained as preloading a webpage when you are switching tabs.
The intention by Mozilla with Tab Warming is to speed up tab switching process by improving the performance of switch from one tab to the next. Usually, Firefox does a decent job when it comes to tab switching, but some websites do have some noticeable delays when you are switching to them from another tab on Firefox browser.
Particularly pages using SVGs and CSS for animation, they tend to have a noticeable lag when you switch to them from another tab. As it stands, when you are viewing one tab and move your cursor to point at the next tab, Firefox will begin to render the page in the background before you click the tab.
By doing so, Firefox gains the time it takes to load up the webpage, as it began loading the page in the background the second you moved the cursor to that tab before clicking on it. Mozilla explains it as follows:
With tab warming enabled, when you hover over the tab with your mouse cursor, the rendering of that sophisticated SVG will occur while your finger is still on its way to click on the mouse button to actually choose the tab.
| Tab Switching Enabled | Tab Switching Disabled | |
| Hover mouse and click | Webpage loading delays either reduced or eliminated | You may notice some delays especially if SVG and CSS used for animations |
| Hover your mouse but don’t click | There will be minimal upsurge in device’s resource use | There will be no changes |
Tab warming feature is not enabled by default in the browser. It is currently only supported by Firefox Nightly and to use the feature, you have to enable it manually by typing the following code in the address bar:
about:config?filter=browser.tabs.remote.warmup.enabled
Hit Enter key the double-click on Preference. If it has the value ‘True’ that would mean Tab Warming has been enabled. If the value is ‘False’ it is disabled. If you want to use the feature, check on the ‘True’ value. You should also appreciate the fact that web page loading speed is subject to other factors also; your internet connection speed, and your device’s capabilities playing a big part as well.
