latest firefox is continuously refreshing the page on a Website, both Windows11 and Linux versions. Website loaded ok previously and still loads ok using Chrome. Why?

Hi, could you please share a URL?

That would be difficult. It's a customer portal only reached after logging-in, and contains sensitive data. The public landing page is fine, and so are subsequent pages after logging in ( it is possible to stop the continual reloading by clicking the reload/stop button just at the right time ), and then the menus are clickable to select a different page. However, the main (logged-in) menu page is always continually refreshing when returned to. Is there any way I can start to debug this myself?

How big is this site operator? Would it be plausible they're targeting different browsers with different code versions? Does anything change if you use "Chrome Mask" extension? For separate, isolated investigation, would you be able to grab a copy of Firefox Nightly nightly.mozilla.org and use that for testing, to potentially eliminate any profile factors, and have a separate "factory" setup on the side — if it also reproduces in that fresh Nightly?

The site operator is a small holiday booking company. As mentioned, it's only when we login to the owner's section of the site that the menu page there continually refreshes. It only started in the last couple of weeks or so - I assume due to the upgrade to 152.0. I have tested with Firefox nightly on my Linux PC and can confirm that this also exhibits the same behaviour. Is it possible to downgrade to the previous version (?) - I would like to confirm that the upgrade is the problem. By way of note, the site also continually refreshes on my Android phone (using Firefox).

Yes! Absolutely, the nightlies are a great way to do arbitrary upgrades–downgrades in isolation, so that's a great idea. I've picked one random day from late in the v150 cycle, this is the folder with all the installers: archive.mozilla.org/pub/firefox/nightly/2026/03/2026-03-20-20-32-03-mozilla-central/ — would you be able to pick a binary for your platform out of these?

If you want more systemic approach to this, there's also mozregression — a tool to do all of the above in a more automated fashion for you incl. a desktop app for both Windows and Linux (you tell it a version or date range to download and launch for you with ephemeral profiles one by one to verify the same scenario across versions — potentially helping to narrow down any impactful change to just the exact changeset). I've posted some instructions for this recently here with pictures included if you ever need these.

Yep - progress. I extracted - firefox-150.0a1.en-US.linux-x86_64 - and it works just fine. No continuous refreshing. It did "Blink" once - quite noticeably - as it displayed the owner page, and I thought it was going to go into continuous refresh, but no, all OK. I'm now just being paranoid! So yes, version 150 is OK. I am happy to look into this further but am a bit busy at the moment so if there is more to look into then please let me know, but the feedback will be a bit slower. Many thanks, Jeremy

Oh wow that's definitely intriguing! I did check if there are any recent bugs filed using a few relevant keywords to save investigation effort since this sounds like a regression, and came back empty handed. Since you're potentially the only one with access to the reproduction example (as I doubt they'd have a publicly accessible demo for their platform, that could be used to see it exhibit this way too?) it would be greatly appreciated if you could assist narrowing down the regression window.

The mozilla.github.io/mozregression site has some info and a video, but I also recently documented this process for support.mozilla.org/questions/1589917#answer-1829099 you can glance for inspiration — I annotated some of the screens there, you can either go for a default empty profile and sign back in each time, or use the "clone-first" option I mentioned there to keep your cookies/session between the test runs so you don't have to sign back in constantly, keep the other contraptions default (as you reproduce in default blank slate, so you don't have to complicate the runs), just select the release versions as "good" 150, "bad" 153 and let it run — it should start opening up individual versions and as it narrows the range from both sides you should ideally see it alternating between some "bad" and some "good" versions — to hopefully land on the culprit, in case it's not "just" intermittent of sorts or flaky on the site side.

OK, so I have run mozregression and it has found a result. How do I report the findings, or has it all been uploaded to you already? For what it's worth, the final few lines are:

2026-07-07T09:29:38.535000: DEBUG : Found commit message: Bug 2034984. In the jxl decoder make sure to apply color management before premultiplying alpha. r=saschanaz

Differential Revision: https://phabricator.services.mozilla.com/D297307

2026-07-07T09:29:38.536000: DEBUG : Did not find a branch, checking all integration branches 2026-07-07T09:29:38.536000: INFO : The bisection is done. 2026-07-07T09:29:38.537000: INFO : Stopped

Cheers, Jeremy

Thanks Jeremy, this one's a little weird as that pertains to images (but that gives me some things to try to test separately) — would you have any of the logs, results or screen shots of these from the few last steps, e.g. "Narrowed regression window to ID#1, ID#2, ID#3 ~ 3 steps left" or something similar, to see the bigger context around the change? (Or, basically, to save your last IDs for "last good" and "first bad" for posterity to add to the ticket later?)