Websites or add-ons incorrectly report incompatible browser

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Add-ons and some websites require that you use a specific browser, and cause the following problems:

  • Websites report that your browser is incompatible, or suggest that you upgrade your browser.
  • You are not able to install extensions or themes from Addons.Mozilla.org because you see one of the following messages, even though your version of Firefox is listed as compatible.
    • This add-on is for older versions of Firefox
    • Upgrade Firefox to use this add-on

Note: Some websites or add-ons may be legitimately incompatible with your version of Firefox.

If you have already verified that the website or add-on is compatible with your version of Firefox, the cause of the problem may be in your Firefox "User Agent" string, that identifies your browser type to websites. Common causes of this problem are installing Megaupload Toolbar extension or Creative ZENCast plugin and then updating Firefox. This article describes how to reset your user agent to remedy these problems.

Reset your user agent

To reset your user agent:

  1. In the Location bar, type about:config and press EnterReturn.
    • The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise!, to continue to the about:config page.
  2. Search for useragent by typing it into the Filter field.
  3. Right-clickHold down the Ctrl key while you click on each of the three preferences listed below and select Reset from the context menu.
    • general.useragent.extra.firefox
    • general.useragent.locale
    • general.useragent.security
  4. If they exist, you may also need to reset:
    • general.useragent.extra.productName - where productName can be the name of some third party software (e.g. microsoftdotnet).
    • general.useragent.override

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

3.5/3.6:
  1. At the top of the Firefox windowOn the menu bar, click Tools, then select Clear Recent History....
  2. In the Time Range to clear: drop-down, select Everything.
  3. Click the arrow next to Details to display the list of items that can be cleared.
  4. Select both Cookies and Cache.
  5. Click Clear Now.

3.0:
  1. At the top of the Firefox windowOn the menu bar, click Tools, then select Clear Private Data....
  2. Select both Cookies and Cache.
  3. Click Clear Private Data Now.

If resetting the above preferences does not work

If resetting the above preferences does not work, see:


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