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Why does Firefox 18.0.1 try to see the .m4b I'm trying to download as an .mp4?

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I'm trying to download an .m4b (Apple Audiobook format) file on my Macbook Pro (OS 10.8.2) with Firefox 18.0.1. When I do, Firefox opens a new tab like it's going to download the file, but then loads the m4b into what I assume is the Quicktime plugin for Firefox and starts playing it. When I mouse over the tab, the tip that pops up says:

"filename.m4b (video/mp4 Object)"

I tried it on my iMac (OS 10.8.2) running Firefox 17.0.1 and the file downloaded correctly as an m4b. What gives?

I'm trying to download an .m4b (Apple Audiobook format) file on my Macbook Pro (OS 10.8.2) with Firefox 18.0.1. When I do, Firefox opens a new tab like it's going to download the file, but then loads the m4b into what I assume is the Quicktime plugin for Firefox and starts playing it. When I mouse over the tab, the tip that pops up says: "filename.m4b (video/mp4 Object)" I tried it on my iMac (OS 10.8.2) running Firefox 17.0.1 and the file downloaded correctly as an m4b. What gives?

All Replies (2)

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In the Applications category of the Preferences window, check if you have an entry for video/mp4. If it's there, make sure it's not set to “Use QuickTime Plug-in (in Firefox)”.

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I tried that (just now). I have a Video-MPEG4 entry that I set to Always ask, and a QuickTime Player.app Document (video/mpeg), but none at all that have video/mp4.