From MozillaZine Knowledge Base

This article describes how Firefox and Mozilla Suite/SeaMonkey handle downloads for different types of files and how you can change that behavior. If you need help with embedded media on a web page or a "missing plugin" alert, see Video or audio does not play. If you need help with Thunderbird mail attachments, see Actions for attachment file types.

This article has not been fully updated for Firefox 3 or SeaMonkey 2 (not yet released at time of writing). Both will include a new system of managing download actions and helper applications. [1]

Opening dialog

When you click a link to download a file, the MIME type determines what action is taken. If you see an "Opening <filename>" dialog asking if you want to save the file or open it with a specified application, that means that no plugin exists that can handle that MIME type and you have not previously selected a download action or helper application to always use for that type of file.

If you check the option to "Always perform this action when handling files of this type" (SeaMonkey and Mozilla Suite) or "Do this automatically for files like this from now on" (Firefox), then an entry will appear for that type of file in the SeaMonkey/Mozilla Suite "Helper Applications" or Firefox "Download Actions" listing.

In certain situations, you may not be able to set an automatic download action because the choice to automatically perform the action for future downloads will either not be remembered or the option will be "grayed-out", as shown in this SeaMonkey example. This problem can occur when a misconfigured web server incorrectly sends the file with the MIME type "application/octet-stream" or "text/plain". It also can happen if the server assigns "Content-Disposition: attachment" to the download [2].

Changing download actions

This will not affect media embedded in a web page - only links to the files themselves.

Certain file extensions may include multiple entries, one for each MIME type associated with that type of file.

Firefox

Firefox 2: Go to "Tools -> Options -> Content / File Types -> Manage...".

Firefox 1.5: Go to "Tools -> Options -> Downloads / Download Actions -> View & Edit Actions".

The Download Actions window will open. (MIME types are not shown by default. Click the icon in the top right corner and select "MIME Type" to display them.)

Select a file type entry and click 'Change Action...'

• If you want files of that type to open with the default application, select "Open them with the default application".
• If you want a different application to handle that type, select "Open them with this application" and choose the application. Caution: Make sure that the application you choose can handle the file type. For example, to choose Windows Media Player, browse to the C:\Program Files\Windows Media Player folder in the "Select Helper Application" window and select "wmplayer.exe".
• If you want the file to be saved instead of opened, select "Save them on my computer".
• In some cases, the option "Use this Plugin" will be available. It is the default action if a plugin is found for the file type.

SeaMonkey and Mozilla Suite

Go to "Edit -> Preferences -> Navigator -> Helper Applications". The Helper Applications preferences panel will open.

The entries will be listed as MIME types. Select the entry for the download action you wish to change and click the 'Edit' button to change the download action.

• If you want files of that type to open with the default application, select "Open it using the default application"
• If you want a different application to handle that type, select "Open it with" and use the "Choose..." button to locate the program executable.
• If you want the file to be saved instead of opened, select "Save it to disk".

Note that SeaMonkey and Mozilla Suite do not list plugin actions in the Helper Applications listing. You cannot disable a plugin for file downloads here, as you can in the Firefox Download Actions listing. You can check in "Help -> About Plug-ins" to see which MIME types are automatically handled by plugins.

Adding a download action

SeaMonkey and Mozilla Suite

The Helper Applications preference panel (shown above) allows you to add new download actions for MIME types. Clicking the "New Type..." button opens a dialog where you can add the MIME type (e.g. application/msword) description (e.g. Word Document) and file extension (e.g. doc). You can set the new download action to either open with a specified helper application or save to disk.

The actions you add will not affect MIME types that are handled internally, which include certain MIME types such as image/jpeg or text/plain [3] and all MIME types that are handled by plugins [4]. Before adding a new action for such MIME types, a Warning dialog similar to the following will be displayed:

Firefox

In Firefox, MIME types that are not handled by plugins do not appear in the Download Actions listing unless you have previously encountered that type of file and checked the option in the "Opening" dialog box to "Do this automatically for files like this from now on", as described above. You cannot add new file types to the Download Actions listing in Firefox, as you can in Mozilla Suite and SeaMonkey. The MIME Edit extension provides the Mozilla Suite/SeaMonkey "Helper Applications" interface as a Firefox add-on.

Removing a download action

After a helper application or "save to disk" download action has been set, that action will be taken automatically for those types of files. To remove a download action, open the Download Actions dialog or the Helper Applications preference panel as described above, select the file type entry and click the "Remove action" or "Remove" button. The next time you encounter that type of file, an "Opening" dialog will appear, asking you to specify an application or save the file.

Removing a download action does not affect files that are handled by plugins. Mozilla browsers will automatically use a plugin if it is available for the MIME type, as shown in the about:plugins list.

Resetting download actions

If problems arise or if you want to restore the default set of file download actions, do the following [5]:

1. Type about:config into the address bar.
2. Find the preference browser.download.pluginOverrideTypes and, if it is present, right-click on it and select reset.
3. Find the preference plugin.disable_full_page_plugin_for_types and, if it is present, right-click on it and select reset.
4. Exit the browser, then open the profile folder (Windows 2000/XP/Vista users, read this for help finding it).
5. Delete (or rename) the file mimeTypes.rdf. Caution: There is also a mimeTypes.rdf file in the program folder. Do not delete it by mistake.

File handling in Firefox 3 and SeaMonkey 2

In Firefox 2 and SeaMonkey 1.x or earlier, you can't remove download actions for file types currently handled by plugins, unless you disable or reconfigure the plugin (see Issues related to plugins for details). In Firefox 2 you can change the action to save the file or open it with an external application but removing that action just restores the plugin as the handler for that MIME type (as shown in about:plugins).

Starting in Firefox 3 and SeaMonkey 2, you will be able to disable plugins within your browser, via "Tools -> Add-ons (or Add-on Manager) -> Plugins".

You will also be able to use "Tools -> Options -> Applications" in Firefox 3 or "Edit -> Preferences -> Browser -> Helper Applications" in SeaMonkey 2 to change the action for any of the listed content types (Web Feeds and certain protocols will also be listed). The new interface will have a drop-down menu to change content handling for each listed type. You will be able to remove an automatic download action for file types currently handled by plugins by selecting "Always Ask". Plugins are identified with "(in Firefox)" or "(in SeaMonkey)" after the handler name. For example, here is an image showing the Applications Options window in Firefox 3 and the drop-down menu for the "Adobe Acrobat 7.0 Document" type, with "Use Adobe Acrobat (in Firefox)" selected and other options for handling PDF files.

Note: The new (Helper) Applications window does not include file extensions (such as .PDF) and MIME types are only included for content types with multiple entries. You will have to depend on the icon or the content description to determine the type of file. Additionally, you won't be able to add entries for new content types, as you were able to do in Mozilla Suite/SeaMonkey 1.x.

See also

• Page displays as gibberish
• The associated helper application does not exist
• Download Actions list is empty
• Open File dialog has the OK button grayed out
• Streaming media
• Opening files using plugins

Related bug reports

Please do not comment in bug reports unless you are helping to fix the bug. Also note that some of the bugs listed below are fixed and others may be marked "invalid" or "wontfix"; these are included for informational purposes only.

• Bug 58554 – Support using external programs to show non-inlined images and other content
• Bug 201546 – Can't hide opening dialog if download filetype is application/octet-stream
• Bug 236541 – "do this automatically for files like this" doesn't work when Content-Disposition:attachment is used
• Bug 250914 – Clicking on WMV file opens What should Firefox do? dialog
• Bug 264492 – OK button in (open with/save to) window is greyed/grayed/disabled when certain mimeTypes.rdf entries exist
• Bug 315536 – "do this automatically for files like this from now on" often grayed out (note comment #48)
• Bug 347230 – Minimal "Save"-only dialog shown for files with discoverable types (known file extensions)
• Bug 377784 – create an easy-to-use MIME-type configuration system

External links

• Managing file types (Firefox) at support.mozilla.com
• Helper Applications at mozilla.org