After 1.17.7b, zen browser is extremely slow

[red-crate]

Preliminary Checks

• [x] I have read and understood the important section above.
• [x] I have searched existing issues and avoided creating duplicates.
• [x] I am not filing an enhancement request.
• [x] I have checked that this issue cannot be reproduced on Mozilla Firefox.
• [x] I have checked that this issue can be reproduced once I removed all my Mods and Custom CSS.

What happened?

I suspect the issue comes from the Firefox 145 base used in 1.17.7b. I reverted to 1.17.6b (based on 144.0.2?), and everything is fine.

The main symptom in 1.17.7b isnt constant slowness. It works fine at first, but then randomly freezes or hangs on certain tabs. It just stops loading completely, forcing me to use another browser. Changing hardware acceleration settings made no difference

Expected behavior

just browsing fast

Actual behavior

freezing or page load slowly

Steps to reproduce

Update to 1.17.7b or 1.17.8b from 1.17.6b

Screenshots and videos

i make new profile and test

here is profiler text : https://share.firefox.dev/4463d80 with no extensions

Version

1.17.7b

What platform are you seeing the problem on?

Windows - x64

What component is this issue related to?

Other

Relevant log output if applicable

[Propheticus]

Your profile recording is full of these:

First some basic troubleshooting to try to fix these timeouts:

• Confirm in the (Windows) Firewall that Zen is allowed UDP traffic. Example from the "Windows defender firewall with advanced security" on the inbound rules list:

  

• Renew your network connection. Use the ipconfig /release and ipconfig /renew commands one by one in a command prompt (CMD). Then restart the PC.

  

• Clear the browser's DNS cache on the about:networking page > DNS section.

  

If all that doesn't help

Could be related to https://bugzilla.mozilla.org/show_bug.cgi?id=1878510

You can try setting network.http.http3.enable to false in about:config

[red-crate]

Your profile recording is full of these:

First some basic troubleshooting to try to fix these timeouts:

* Confirm in the (Windows) Firewall that Zen is allowed UDP traffic. Example from the "Windows defender firewall with advanced security" on the inbound rules list:
   <img alt="Image" width="1101" height="70" src="https://private-user-images.githubusercontent.com/6628064/517694967-7940d0e8-f446-4c60-a7f4-11e44d9de849.png?jwt=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.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.RYLdM9xrPWGtfI6Kg0faIiH_ZIwME8L8ZVAtot7lQMI">

* Renew your network connection. Use the `ipconfig /release` and `ipconfig /renew` commands one by one in a command prompt (CMD). Then restart the PC.
   <img alt="Image" width="210" height="33" src="https://private-user-images.githubusercontent.com/6628064/517695221-8600d763-d722-4c8f-91d5-f5d506b5c95a.png?jwt=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJnaXRodWIuY29tIiwiYXVkIjoicmF3LmdpdGh1YnVzZXJjb250ZW50LmNvbSIsImtleSI6ImtleTUiLCJleHAiOjE3NjM4MzY3MzAsIm5iZiI6MTc2MzgzNjQzMCwicGF0aCI6Ii82NjI4MDY0LzUxNzY5NTIyMS04NjAwZDc2My1kNzIyLTRjOGYtOTFkNS1mNWQ1MDZiNWM5NWEucG5nP1gtQW16LUFsZ29yaXRobT1BV1M0LUhNQUMtU0hBMjU2JlgtQW16LUNyZWRlbnRpYWw9QUtJQVZDT0RZTFNBNTNQUUs0WkElMkYyMDI1MTEyMiUyRnVzLWVhc3QtMSUyRnMzJTJGYXdzNF9yZXF1ZXN0JlgtQW16LURhdGU9MjAyNTExMjJUMTgzMzUwWiZYLUFtei1FeHBpcmVzPTMwMCZYLUFtei1TaWduYXR1cmU9YThjZWIwMzlkYzllY2MzMDhiYWM4MGYzOWNmZjZlNTg5ZGM1M2E0YjNkM2Y0YzMxYjM4YWEzMTM5YmQzOWY5ZSZYLUFtei1TaWduZWRIZWFkZXJzPWhvc3QifQ.ujcDESUVv2DqG0td6kuYTVklLilfTNBxSlsSCwawHMk">
   <img alt="Image" width="186" height="32" src="https://private-user-images.githubusercontent.com/6628064/517695263-444830dd-b0ff-4c1f-8cf9-72b6992281e8.png?jwt=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.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.wzZJBAvl3y08YvhAou5vPzOVlD1DqCHg6uzRgRtLjNk">

* Clear the browser's DNS cache on the `about:networking` page > DNS section.
   <img alt="Image" width="533" height="241" src="https://private-user-images.githubusercontent.com/6628064/517695406-baf0c839-5742-4933-95f5-469fad4fbb6f.png?jwt=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJnaXRodWIuY29tIiwiYXVkIjoicmF3LmdpdGh1YnVzZXJjb250ZW50LmNvbSIsImtleSI6ImtleTUiLCJleHAiOjE3NjM4MzY3MzAsIm5iZiI6MTc2MzgzNjQzMCwicGF0aCI6Ii82NjI4MDY0LzUxNzY5NTQwNi1iYWYwYzgzOS01NzQyLTQ5MzMtOTVmNS00NjlmYWQ0ZmJiNmYucG5nP1gtQW16LUFsZ29yaXRobT1BV1M0LUhNQUMtU0hBMjU2JlgtQW16LUNyZWRlbnRpYWw9QUtJQVZDT0RZTFNBNTNQUUs0WkElMkYyMDI1MTEyMiUyRnVzLWVhc3QtMSUyRnMzJTJGYXdzNF9yZXF1ZXN0JlgtQW16LURhdGU9MjAyNTExMjJUMTgzMzUwWiZYLUFtei1FeHBpcmVzPTMwMCZYLUFtei1TaWduYXR1cmU9ZjFjY2EzOThjMzIxMTM5NTdjZGI3NTU4Njc4OTcxZTJhOTczNzZlNzI2NTIwOTgwYjdjMjNjMjAwZTMzMTIzYyZYLUFtei1TaWduZWRIZWFkZXJzPWhvc3QifQ.52z0zMqHYT8Xnj27fyqO4n7lfCUszklgisgC33PiNVw">

If all that doesn't help

Could be related to https://bugzilla.mozilla.org/show_bug.cgi?id=1878510

You can try setting network.http.http3.enable to false in about:config

still slow, network.http.http3.enableis already true

[Propheticus]

network.http.http3.enableis already true

But I said you should try setting it false

[red-crate]

network.http.http3.enableis already true

But I said you should try setting it false

Oh it was a problem. now zen is really fast again. maybe firefox 145 has http/3 performence issue.

[Propheticus]

@red-crate

Wonder what changed between 144 and 145 in that regard. Perhaps this change in the enhanced tracking protection?

Have you got these 'unbreak' options enabled?

It can also be a (filtering / blocking) proxy or something else in your network stack doesn't like http/3 or is failing to use DNS over HTTPS (DoH).

If you use a network (router?) or system-wide filtering solution, make sure it's set up (and supports) http/3 You can also try disabling DoH in Zen.

[red-crate]

@red-crate

Wonder what changed between 144 and 145 in that regard. Perhaps this change in the enhanced tracking protection?

Have you got these 'unbreak' options enabled?

It can also be a (filtering / blocking) proxy or something else in your network stack doesn't like http/3 or is failing to use DNS over HTTPS (DoH).

If you use a network (router?) or system-wide filtering solution, make sure it's set up (and supports) http/3 You can also try disabling DoH in Zen.

I using "standard", never change

I using adguard desktop app, maybe this will affect, but 144.0.2 / other browser was fine, 145 is like that.

[umarhamzy]

This issue is still relevant (as at 17.7.9b), just updated to .10b, will test and see how it goes.

When this happens, memory usage spikes up to 9,000+ MB from around 2,500MB

[Propheticus]

@umarhamzy High mem usage is a different issue than the one reported here. This is about slowness when using https/3 possibly in combination with filtering software (proxy/man in the middle) like adguard.

High memory reports can be made here: https://github.com/zen-browser/desktop/issues/8932 With the info provided there it's a bit easier to spot possible causes, either a website, extension or Zen process leaking memory.

[BnDLett]

I was having issues with browsing performances (first loads of websites were extremely slow, up to 5-10 seconds to start seeing anything), and it does seem like changing the network.http.http3.enable config to false fixed the issue.

[Propheticus]

Possibly related: https://bugzilla.mozilla.org/show_bug.cgi?id=2001618 https://bugzilla.mozilla.org/show_bug.cgi?id=2002061

[red-crate]

I saw 1.17.11b update about this issue. maybe "Fixed very slow page loading in cases where http/3 connections failed but did not properly fall back to http/2.".

but after 1.17.11b, browser is still slow. network.http.http3.enable to false is solution.

[Propheticus]

I suspect it might have a relationship to adguard. Do you have the same issue when you try in Firefox?

[red-crate]

I suspect it might have a relationship to adguard. Do you have the same issue when you try in Firefox?

Yes, Firefox has the same issue.

I tested some scenarios: downgrading Firefox to 144.0.2 (or Zen to 1.17.6b) restores the speed fast. removing AdGuard also fixes the issue.

However, setting network.http.http3.enable to false worked perfectly with the recent Zen/Firefox versions, so Im using that now.

[Propheticus]

If you care enough it'd be good to report to AdGuard that their app seems to conflict with newer Firefox http/3 support.

https://github.com/AdguardTeam/AdguardForWindows/issues

Of course first check if the desktop app doesn't have options to support DNS over HTTPS on http/3 and such. Maybe it's a configuration issue.

Could this issue possibly be related? Symptoms sound similar https://github.com/AdguardTeam/AdguardForWindows/issues/5755

[Propheticus]

@red-crate Hi, I've reported the issue to Mozilla because this is an inherited issue from Firefox. A dev has asked for more information. Since I cannot reproduce the issue myself, would you be able to help out?

Please recreate the issue once more with logging* in the new profile without extensions you had created (or another) with http/3 enabled.

To make a logging file either follow the steps below or valenting's tip:

• open about:logging and then

1. Set preset to http/3
2. Log to a file
3. Pick a good location to save the files (take note where)
4. click 'Set Log File'
5. click 'Start logging'
6. Recreate the issue for a short while (don't log for too long or the file will become huge, triggering the issue once is enough)
7. click 'Stop logging'
8. navigate to the folder from step 3 and zip it (or gz, 7z is not supported on GitHub). The file it looks like log.txt-main.8040.moz_log
9. upload the file here or directly in the bugzilla issue if you want

Thanks in advance!

[valenting]

Actually, you can use this link to capture the profile:

about:logging?modules=timestamp%2Csync%2CnsHttp%3A5%2CnsSocketTransport%3A5%2CnsHostResolver%3A5%2Cneqo_http3%3A%3A*%3A5%2Cneqo_transport%3A%3A*%3A5&preset=http3&output=profiler&profilerstacks=&profiler-preset=networking

Note the profile might contain some private information, so you might want to send it privately via email to [email protected] - please reference https://bugzilla.mozilla.org/show_bug.cgi?id=1997372 in the email.

Thanks!

[mr-cheffy]

Sorry

[zFgVn-1]

same issue on arch linux btw

[Propheticus]

@zFgVn-1 Could you share a network log made while triggering the issue? This could help the Firefox devs find what causes this. See https://github.com/zen-browser/desktop/issues/11390#issuecomment-3602657107