Change Useragent string without addon (Mozilla browsers)

Why some webpages deny access because I'm not using one of the top four browsers is beyond me...

Anyhow, here's how you can spoof your useragent on all Mozilla-based (Firefox-like) browsers, e.g. Seamonkey, Palemoon etc. - and of course Firefox itself:

• Enter about:config in your URL bar.
• Search for "useragent" and make sure you don't already have the required field (or others that might interfere).
• If not, create a new string entry by right-clicking inside the Preferences list, and call it general.useragent.override.
• Enter a suitable value. How about Firefox 78 for Windows: Mozilla/5.0 (Windows NT 10.0; rv:78.0) Gecko/20100101 Firefox/78.0
• You can check a Mozilla browser's current User Agent under about:support

That's it. According to Mozilla, it might be necessary to do some resetting to make sure the new value takes.
Make sure privacy.resistFingerprinting isn't set to true!

Where to get an up-to-date useragent string? ∆

Searching "useragent", many sites are outdated or just phishing.
Here are some that look slightly better and up-to-date:

• https://udger.com/resources/ua-list
• https://techpatterns.com/downloads/firefox/useragentswitcher.xml (download or view source)

What's your browser's current Useragent string? ∆

sh
netcat -l -p 8100 -v
#or
ncat -k -l -p 8100 -v

Then open your browser to http://127.0.0.1:8100/ and watch the terminal output.