How to reset the default user agent on Firefox

A ''user agent'' is a line of code that tells websites what type of browser and operating system you're using. This information helps the web server deliver content that's compatible with your browser. You can change Firefox's user agent to trick outdated websites into thinking that you're using a different version of the browser. Web developers might do this to see how their websites will appear on different versions of a browser. Sometimes, add-ons and other installations can change your user agent without your knowledge. In any case, it's important to switch it back to the ''default user agent'' to display most websites correctly. To reset your user agent: # [[T:aboutconfig]] # Search for '''useragent''' by typing it into the '''{for not fx11}Filter{/for}{for fx11}Search{/for}''' field. # [[T:contextmenu]] on each of these preferences, if they exist, and select {menu Reset} from the context menu. * {pref general.useragent.extra.firefox} * {pref general.useragent.extra.''productName''} - where ''productName'' can be the name of some third party software (e.g. ''microsoftdotnet''). * {pref general.useragent.locale} * {pref general.useragent.override} * {pref general.useragent.security} [[Image:reset_ua1.png]] After resetting your user agent, you may need to clear your cookies and cache: [[T:clearCookiesCache]] [[T:ShareArticle|link=mzl.la/1vqKUTW]]

A user agent is a line of code that tells websites what type of browser and operating system you're using. This information helps the web server deliver content that's compatible with your browser.

You can change Firefox's user agent to trick outdated websites into thinking that you're using a different version of the browser. Web developers might do this to see how their websites will appear on different versions of a browser. Sometimes, add-ons and other installations can change your user agent without your knowledge. In any case, it's important to switch it back to the default user agent to display most websites correctly.

To reset your user agent:

1. Type about:config in the address bar and press EnterReturn.
   A warning page may appear. Click Accept the Risk and Continue to go to the about:config page.
2. Search for useragent by typing it into the FilterSearch field.
3. Right-clickHold down the control key while you click on each of these preferences, if they exist, and select Reset from the context menu.

• general.useragent.extra.firefox
• general.useragent.extra.productName - where productName can be the name of some third party software (e.g. microsoftdotnet).
• general.useragent.locale
• general.useragent.override
• general.useragent.security

After resetting your user agent, you may need to clear your cookies and cache:

1. Click the menu button to open the menu panel.
2. Click History and select Clear Recent History…
3. In the Time Range to clear: drop-down, select Everything.
4. Below the drop-down menu, select both Cookies and Cache. Make sure other items you want to keep are not selected.
5. Click OKClear Now.