Custom UserAgent String is an extension that enables you to easily change your browser user-agent by adding site-specific user-agent strings from the Options page (add-on's control panel).
Some important features:
1. Add a custom user-agent string for each URL or website (domain).
2. There is an option to change each URL to a domain from the control panel.
3. Toolbar button serves as an ON or OFF switch to quickly turn the add-on ON or OFF.
4. User-agents can be added in the options page (more than 100 sample user-agent strings are also provided).
5. For each user-agent string, you can either delete or disable it for future use.
6. To find a user-agent string you can either use a Google search (there are plenty of websites that provide a free UA list) or use the sample list provided in the add-on's control panel. This list includes more than 100 UAs for modern browsers and ranging from desktop to mobile platforms. This list is also available in this (http://mybrowseraddon.com/custom-useragent-string.html#faq) FAQ section.
Note: in order to report bugs, please visit add-on's homepage (http://mybrowseraddon.com/custom-useragent-string.html) and fill the bug report form.