After some time Tor Browser always goes to 100% cpu, might be due to NoScript going wrong

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  1. I’m on Debian Trixie (up to date).
  2. I get Tor via the Tor repo (currently up to date and 15.0.15).
  3. Security level : standard.

So, I fire up Tor, use it.

I open tabs, close them, do stuff.

In the end, typically after maybe a day, I’m not sure what causes it, Tor goes to 100% on one processor.

Closing all tabs does not fix this.

I’ve once then gone to Web Developer Tools, then Performance, then “start recording”.

Looking at the info on the profiler site, which I’ve done once, it looked to me like the code I was looking at was related to, or was, the NoScript plugin - but this is hardly an authoritative diagnosis.

This is kinda of a deal-breaker, because currently the fix is closing and re-opening Tor, but I have like half a dozen sites which require log in work, which I normally have open.

Usernames, passwords, sometimes an email I have to receive, click on link, approve IP, then go around and log in again, and/or 2FA from the phone. Six times. Every time I start Tor.

Getting back up to normal from a cold start is enough work that you won’t do it on a daily basis, which means you can’t use Tor for sites needing a login - you’d have to use Firefox, and Tor for normal browsing, but that’s not how it goes - you end up using Firefox for everything because it’s there.

I note if Tor allowed me to white-list cookies across reboots, this would not be a problem.

I wholly understand the security rationale for this, but it has a serious impact on usability normally and in this case combines with browsers being a bit fragile to cause a fundamental problem. Perhaps it should be an option.

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One thing I would try to separate first is “Tor Browser itself is busy” from “one site/script keeps NoScript/Firefox busy after it has run for many hours”.

When it happens, before restarting, open about:processes in a new tab and see whether the high CPU is the main process, a content process, or an extension process. If it points to an extension/NoScript process, a Firefox profiler capture would probably be useful for the Tor Browser devs. If it points to one site/content process, closing that tab may not be enough if a worker is still alive, so a New Identity or restart is the clean test.

I would avoid trying to make Tor Browser remember normal login cookies as the workaround, because that works against one of its main protections. For accounts that must stay logged in all day, it may be less frustrating to keep them in a separate Firefox profile and use Tor Browser for the things where you need Tor’s isolation.

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open about:processes in a new tab

Thank you. I did not know about this. I shall do so.

it may be less frustrating to keep them in a separate Firefox profile

Firefox is faster and easier to use than Tor. If Firefox is open, I find it tends to get used rather than Tor.