User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:33.0) Gecko/20100101 Firefox/33.0 Build ID: 20141106120505 Steps to reproduce: With the latest version of Firefox (33), I want to execute a testcase through firefox, which should auto save a text/plain mime type. At first, I couldnot find the text/plain mime listed under Options -> Application -> Content Type. So I edited the mimeType.rdf file. After this change, I could see the 'TXT file' content type getting listed under Options -> Application -> Content Type. I added the following lines to mimeType.rdf file: <RDF:Description RDF:about="urn:mimetype:handler:text/plain" NC:saveToDisk="true" NC:alwaysAsk="false" /> <RDF:Description RDF:about="urn:mimetype:handler:text/plain" NC:saveToDisk="true" NC:alwaysAsk="false" /> and under <RDF:Seq RDF:about="urn:mimetypes:root">: <RDF:li RDF:resource="urn:mimetype:text/plain"/> Actual results: I opened a URL that should render a txt file (https://wordpress.org/plugins/about/readme.txt), however it didnot autosave. Expected results: It should have auto saved the txt file to a location I set in the pref.js file

What makes you think that you can override an internal supported content-type by something in mimetypes.rdf ?

I dont know. I did a lot of google, but couldn't find a better solution. Please let me know what should be done to make this work. Thanks.

(In reply to Matthias Versen [:Matti] from comment #2) > > *** This bug has been marked as a duplicate of bug 58554 ***

Why do you reopen this bug report ? bug 58554 is about the same issue and it shows that it's currently not possible to override internal supported mime-types