How to change the UserAgent in Firefox

As the title says... Specially on problematic sites such as YouTube

 

According to @nicolaasjan 's post I've just read after creating this thread , it says and quote:

To change the user agent for YouTube:

• Go to `about:config`.
• Paste `general.useragent.override.youtube.com` in the box (without the quotes).
• Check `String`.
• Click on `+`.
• Enter this in the box:

Code:

Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/119.0.0.0 Safari/537.36

• Click the check-mark.

But I can't guarantee it will keep working, as others have seen the page load slowing on Chrome as well.


Doesn't uBO counter it for you?
If not, carefully follow the instructions here.

You could also test these filters:

Code:

www.youtube.com##+js(nano-stb, resolve(1), *, 0.001)
www.youtube.com##+js(set, yt.config_.EXPERIMENT_FLAGS.ab_pl_man, false)
www.youtube.com##+js(set, yt.config_.EXPERIMENT_FLAGS.web_enable_ab_rsp_cl, false)
||googlevideo.com/videoplayback$xhr,3p,method=get,domain=www.youtube.com

 

After watching the domain name in this flag (red letters):

Code:

general.useragent.override.youtube.com

I decided to try the following flag + string in order to make sure FF can override the user agent for specific sites:

Code:

general.useragent.override.whatismybrowser.com
+
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/119.0.0.0 Safari/537.36

Then I went to

Code:

https://www.whatismybrowser.com/detect/what-is-my-user-agent

I've got this in return:

Code:

Mozilla/5.0 (Windows NT 6.1; rv:109.0) Gecko/20100101 Firefox/115.0

It can't override for specific sites.




Adding a string for a general override works though:

Code:

general.useragent.override
+
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/119.0.0.0 Safari/537.36

gives

Code:

Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/119.0.0.0 Safari/537.36

 

have you considered locale issues instead user agent? i dont have any issues with firefox and windows 10/11 on youtube - instant loading, no timeout, what ever.

 

You're absolutely right.
I totally missed that change (in the past it was possible and it still works in the Pale Moon browser).
See:
https://www.ghacks.net/2019/12/11/m...c-user-agent-override-option-from-firefox-71/.
https://bugzilla.mozilla.org/show_bug.cgi?id=1513574.

For site-specific switches you can use this extension.

 

I use this extension, it is quite useful. I only use it for one thing. Set the OS icon on LinuxQuestions.org to Slackware.
I added to my setting in Custom Mode to tell WhatIsMyBrowser.com I am using Window with Safari.

Code:

{
  "www.linuxquestions.org": "${userAgent} Slackware",
  "whatismybrowser.com": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Safari/537.36"
}

 

Thanks. Installed and working fine.

 

User-Agent Switcher and Manager

Is it possible to make Firefox change the user agent automatically at start up only for YouTube?

 

As you can see by my post above, which works only for two sites, you can set the extension to work only on one web site. For example I would enter this for Chrome 119:

Code:

{
  "www.youtube.com": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/119.0.0.0 Safari/537.36"
}

 

Yes, in Options paste this in "Custom":

Code:

{
  "youtube.com": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.6099.63 Safari/537.36"
}

Then press "Save" at the bottom.

(screenshot)

 

Thanks @nicolaasjan and @chrisretusn