All popular browsers offer build-in user agent switchers, so you can change your user agent without installing any extensions. Google Chrome and Internet Explorer both include user agent switchers in their developer tools, while Firefox offers an about:config option.

Websites identify browsers by their user agents. Modify a browser’s user agent and it will appear as a different browser – or even a browser running on another device, such as a smartphone or tablet.

Google Chrome

Chrome 17 added a built-in user agent switcher. Previously, you had to modify Chrome’s command-line options to change its user agent.

The user agent switcher is part of Chrome’s Developer Tools – open them by clicking the wrench, pointing to Tools, and selecting Developer tools. You can also use the Ctrl-Shift-I keyboard shortcut.

Click the gear icon at the bottom right corner of the Developer Tools window to open the Settings pane.

From the Settings pane, enable the Override User Agent option under Network and select a user agent from the list. You can also select Other and enter your own, custom user agent.

This setting is temporary and only persists while you have the Developer Tools window open. Close the window and Chrome will revert to its default user agent.

Internet Explorer

Internet Explorer also has a user agent option in its developer tools. To open them, press F12 or select the F12 developer tools option from Internet Explorer’s Tools menu.

The developer tools will open in a separate pane at the bottom of the window. Click the Tools menu in the developer tools pane, point to “Change user agent string”, and select a user agent from the list.

You can also select the Custom option and add custom user agent strings to the list.

This setting is also temporary. Internet Explorer reverts to its default user agent after it’s closed.

Mozilla Firefox

Mozilla Firefox doesn’t have an easy way to change its user agent without an extension – this option is buried on Firefox’s about:config page. If you want an easy way to change Firefox’s user agent, use the User Agent Switcher extension instead.

To access the about:config page, type about:config into Firefox’s address bar and press Enter. You’ll see a warning – be careful when you change settings here, you could mess up Firefox’s settings.

Type useragent into the filter box. We’re looking for the general.useragent.overridepreference, but it probably won’t exist on your system.

To create the preference, right-click on the about:config page, point to New, and select String.

Name the preference general.useragent.override

Enter your desired user agent as the value of the preference. You’ll have to look up your desired user agent on the web and enter it exactly. For example, the following user agent is used by Googlebot, Google’s web crawler:

Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)

This setting persists until you change it – even if you close and reopen Firefox. To revert Firefox to the default user agent, right-click the general.useragent.override preference and select Reset.

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Safari also has a built-in user agent switcher. Check out our guide to changing your user agent on Safari for more information.