The new beta of the next version of Firefox lets you view two web pages side by side, with a split you can drag with your mouse.
As usual when a new version of Firefox appears, the following version graduates to beta testing. Firefox 148 came out a few days ago, which means that Firefox 149 is now in beta test.
Although they're still in testing and aren't guaranteed to make it through to release, this version brings some handy novelties, such as hardware-accelerated PDF rendering, address autofill in more countries, performance tweaks for WebGL on Windows, and easier sharing. They are all good, but under the surface and not especially visible. The one we're most interested in is very visible: the beta of 149 enables "split view" by default.
The beta of Firefox 149 showing its new two-page split view – and some other tabs
Mozilla's split view has been in testing for a while, but this is the first time it has been on by default. It lets you place two separate tabs side by side inside the Firefox window. You can drag the separator between them where you wish, for instance for one narrow page and one wide one.
A word of warning. You can download the beta from Mozilla's download site and depending on your OS, either rename it or put it in a different directory to keep your current Firefox installation intact.
We recommend that you don't grab the beta yet.
The problem is that you don't just want to preserve the stable released program – you also need to preserve your profile.
If you run the beta, it automatically picks up your current Firefox profile, and by default Firefox won't open a profile that's been modified by a newer version. That means you can't go back: Firefox just shows an error and suggests creating a new profile, which isn't very helpful.
There are various ways around this.
You can make a new testing profile first, set it as default, quit your current version of Firefox and open the beta – then your current profile is safe. A snag is that you don't keep all your bookmarks and so on, and going back is similarly manual.
Or, you can invoke Firefox with the Profile Manager, which may help but is fiddly.
Perhaps the most useful recovery measure: if you didn't keep a copy of your older version's profile, you can launch your old stable version of Firefox from the command line and use the --allow-downgrade switch.
The split view is a handy feature, and it's worth trying out. However, there's good news: so long as you aren't running the ESR version of Firefox, or something based on it such as Waterfox, you can probably try the new feature today. It became available in Firefox 146 in early December 2025, and if you are running Firefox 146, 147, or the current Firefox 148 (at the time of writing), split view is already there – it's just disabled.
To turn it on, type the magic settings URL, about:config, saying "yes" if necessary, and search for browser.tabs.splitView.enabled. You should find that it's there, but set to false. Double-click it to change that to true. In theory you shouldn't need to, but it's possible you might have to restart Firefox for it to become available.
To try it, select two tabs: click one, then hold down Ctrl – or Cmd on a Mac – and click another. Then, right-click one of them and pick "Open in Split View." The two tabs do not need to be adjacent.
Once you have two open, you will find some new options on the same context menu, such as to separate the split view, or move it to a new group.
It works, and pretty well at that. There's still only one URL bar: click on a pane, and it shows that page's address. They scroll independently, and you don't need to click on them to scroll them. The tab buttons sit side by side in the tab bar, whether it's horizontal or vertical, and tabs can be closed individually just like normal. (In fact, with two close buttons, one in the middle, in testing we often did that accidentally.)
The split view brings the main benefit of a tiling window manager to the browser, which for a lot of us is where we spend the bulk of our time online. Better still, you don't need to learn to use any new or additional tools, and you can just ignore it when you don't need it.
Especially on Linux, a growing number of people already use tiling environments. (This vulture does. We use Rectangle on macOS, and we're becoming quite fond of the Pop!_OS COSMIC desktop, which is already up to version 1.0.8.) If you do, Firefox's version won't bring much benefit.
The arrival of the new feature could be bad news for the Zen browser, though. We looked at this Firefox fork with built-in tiling back in September 2024 and liked it. Since the Chromium-based Arc browser was discontinued in favor of one with built-in automatic plagiarism bots, Zen had less competition – but not any more.
There is still room for improvement, though. Firefox's panes don't act like independent windows, so for instance, you can't just drag a link from one pane to another. You also can't right-click and open in a new pane: it's just a tool for managing existing tabs you already created.
Zen can show four panes at once – such as The Reg and its sibling sites – no problem
At least for now, Firefox can't handle two splits for three separate panes, or a 2×2 layout – things that Zen can do with ease. We'd like to see both Firefox and Zen make it easier to open links in a new pane and things like that.
It's taken 18 months for Mozilla to catch up even just as far as two side-by-side pages. Zen still has quite a significant lead, and room remains for the developers to keep improving and stay comfortably ahead of Mozilla here.
Saying that, Mozilla is on the edge of catching up with the baseline functionality: the simplest and probably the most useful case. We still recommend Firefox as the browser for power users, and it just got better still.
Firefox 149 is scheduled for release on March 24. ®
Source: The register