Comment 269 for bug 25830

Encountered this bug today trying to get a plaintext format (with the mime type `application/<something>`) to display as plaintext in the browser rather than Open With > Firefox (and opening a new window.)

Is there still no workaround for enabling this type of functionality, even by modifying config files in the profile? I tried messing around with `handlers.json` (the file that holds the mime type preferences set in `about:preferences` under the "Files and Applications" header) but had no luck.

Some content types in `about:preferences` permit users to select "Open in Firefox" while others don't. Where is the safelist of permitted content types for this behavior? Could a simple solution to this bug be to add an `about:config` flag that would allow power users to select "Open in Firefox" for any content type?