How To Change Firefox User Agent String?
Sometimes, you might encounter problem of accessing a website, just because the web server doesn’t recognize or allow that web browser (client program) you used to access the site.
Some of you might recall Google Chrome version earlier than 0.4.154.33 encountered problem with Windows Live Mail (a.k.a. hotmail), as the Microsoft free webmail system didn’t properly recognize this new kid :-)
To fix it, the Chrome developers introduced
Now, back to the subject – is it possible to change or overwrite Mozilla Firefox default user agent string, to spoof web server that only flavour particular web browsers? The answer is certainly YES, according to Johne. (I was wrong in an earlier post talking about the same topic :-(
Step to change Firefox user agent string
1) Open Firefox web browser, type
2) You might see some text titled “Here be dragons!”, just click the only button to proceed. Now, you should see a page of Firefox settings (known as Preference). Right click on the page, select New follow by String.
3) In the New String Value dialog box, enter the preference name exactly as
4) The next dialog box appears, this time prompt for a value for the Preference name defined in previous step – enter the user agent string of your choice here:
Now, you should close all the Firefox windows. Upon reopen, the new user agent string specified in

To fix it, the Chrome developers introduced
--user-agent option switch to spoof Live Mail system to believe it’s a “compatible” web client.Now, back to the subject – is it possible to change or overwrite Mozilla Firefox default user agent string, to spoof web server that only flavour particular web browsers? The answer is certainly YES, according to Johne. (I was wrong in an earlier post talking about the same topic :-(
Step to change Firefox user agent string
FYI, these steps are just tested with Firefox 3.5.3:
1) Open Firefox web browser, type
about:config in the address bar and press ENTER.2) You might see some text titled “Here be dragons!”, just click the only button to proceed. Now, you should see a page of Firefox settings (known as Preference). Right click on the page, select New follow by String.
3) In the New String Value dialog box, enter the preference name exactly as
general.useragent.override (as per screenshot) and click OK.4) The next dialog box appears, this time prompt for a value for the Preference name defined in previous step – enter the user agent string of your choice here:
Now, you should close all the Firefox windows. Upon reopen, the new user agent string specified in
general.useragent.override should be effective. To verify it, type about: in the address bar and press enter.
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2010 •
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