1921890 - Browser occasionally does not respond

Status: RESOLVED INVALID

(Firefox for Android :: Performance, defect)

Description

[Denis Müller [:Webworkr]]

User Agent: Mozilla/5.0 (Android 14; Mobile; rv:132.0) Gecko/132.0 Firefox/132.0

Steps to reproduce:

Use Firefox with various tabs.

Actual results:

Since version 130, 131 or 132, the browser reports back that it is no longer responding. You are then asked whether you want to wait or close the app. Compared to previous app versions, this happens much more frequently. In the past, this happened rather rarely. Now it happens quite often.

Comment 1

[eclaudiu64]

I too have encountered this on various sites.

Comment 2

[Kaya [:kaya]]

Our ANR (ApplicationNotResponding) vitals look stable over the last couple of releases. Therefore, I cannot exactly figure out any action items out of this ticket.

Denis Müller and eclaudiu64, can you please provide us some details, such as any specific website that you are encountering this situation consistently, and if possible, any particular extensions you have installed?

fwiw, the situation you're in happens due to the blocked UI thread of the application where you try to perform some UI action (click, press, scroll, zoom etc.) when it is blocked and you get a dialog stating that the application is not responding to your actions due to this busy thread.

Comment 3

[BugBot [:suhaib / :marco/ :calixte]]

The severity field is not set for this bug.
:kaya, could you have a look please?

For more information, please visit BugBot documentation.

Comment 4

[Kaya [:kaya]]

Hi Denis Müller and eclaudiu64,
Are you still experiencing this issue with the similar frequency as you've stated in the bug? Any improvements or worsening in the latest release of Firefox?
(Asking this to confirm once again, as we do not see a regression in our ANR that would have explained the increase in the ANRs you were experiencing. Please see comment 2 above.)

Comment 5

[Denis Müller [:Webworkr]]

In recent weeks I have not been able to observe any more browser freezes. If there is still a need for the list of installed add-ons, I will be happy to provide it.

Nightly
138.0a1 (Build #2016080191), hg-168ba991246a+
GV: 138.0a1-20250319204742
AS: 138.20250318050322

Comment 6

[Denis Müller [:Webworkr]]

Hello Kaya!

What does the abbreviation "ANR" stand for in this context?

Although this abbreviation is used several times in the MozillaWiki, it is not explicitly explained.

Thank you

Comment 7

[Kaya [:kaya]]

Hi Denis,
It stands for "Application Not Responding". This is an Android vital. (details here, if you're curious: https://developer.android.com/topic/performance/vitals/anr)
Basically, it happens when the main thread (UI thread in this case) of the app is not responsive for a few seconds and is busy doing other things. That's why when you perform a click or some gestures on the app, the app freezes and cannot respond (within 5 seconds) as its main thread is busy, and as a result it asks you to either wait (for an indefinite amount of time - possibly enough for main thread to get ready to be used again) or close the app.

Hope this helps. And thank you for reporting back at Comment 5. Please create a new bug ticket if you happen to face such issue again, then we can get into the details in your case.

Please let me know if you have any other questions. Once I hear back, I'll close this ticket.

Comment 8

[Kaya [:kaya]]

Closing ticket based on my last comment and no updates since then. Our ANRs seem stable over the last couple of release. In case the issue is experienced again, please report a new ticket and we will look into it.