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The associated helper application does not exist

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This article deals with the Firefox download error, "(filename) could not be opened, because the associated helper application does not exist. Change the association in your preferences." Firefox stores information about file types and application associations differently than Internet Explorer, which can explain why one would work and not the other.

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Application cannot be located

The "associated helper application does not exist" message can mean that the application that Firefox thinks should open a specific type of file is no longer installed [1]. It can also mean that the application has either been updated or reinstalled and is now in a different location. [2] In such cases, Firefox can not find the application for that file type in the expected location and will issue the error.

You can fix the problem by telling Firefox where to find the program you want to use for the file type. To do this, go to your Firefox menu and change the download action for that file type:

  • Firefox 1.5: Tools -> Options -> Downloads -> View and Edit Actions
  • Firefox 2: Tools -> Options -> Content / File Types -> Manage
  • Firefox 3: Tools -> Options -> Applications

Select the entry in the "Download Actions" or "Applications" list for the file type you're trying to open and change the action to the application that you want to handle that type. Alternately, remove the action (or change the action in the Firefox 3 drop-down menu to "Always Ask"). The next time you download that type of file., select your preferred application in the "Opening" dialog that will appear. See this article for details.

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MimeTypes.rdf file

Firefox stores file type and helper application associations in the mimeTypes.rdf file located in the Firefox profile folder. Sometimes you might not see an entry for the problematic file type in the Download Actions or Applications list or the listing itself might be completely empty. In such cases, exit Firefox, open the Firefox profile folder and remove (or rename) the mimeTypes.rdf file. (Don't delete the "default" mimeTypes.rdf file in the Firefox program folder by mistake.) A new copy of the file will be generated when you restart Firefox. You should then be able to download again without receiving the error but any previously set download actions will be gone.

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See also

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