File types with non-standard extensions opening

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Keightley (US), Simon Q

Dec 19, 2022, 6:27:28 PM12/19/22

I have some end users that are downloading a custom file type (.redars) that are 3D .pdf files that need to open in Adobe in order to function properly. Normally we use the internal pdf reader otherwise so as to make the process as seamless as possible for those not using these .redars files. Up until recently, I’m told that this was working as expected for managed devices that had .redars set to Acrobat and .pdf files set to Firefox, but now Firefox is recognizing these .redars files as .pdf files and following those rules.


Any ideas what could be happening here? I found a couple sort-of-references to this sort of issue on the support site, but the group I’m assisting is having issues understanding what a solution could look like.




Simon Keightley



Mike Kaply

Dec 21, 2022, 2:19:19 PM12/21/22
to Keightley (US), Simon Q,
Are the redars files served with a PDF mime type?

If you go to preferences, is there an entry for redars in Applications?



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Keightley (US), Simon Q

Jan 3, 2023, 10:42:12 AM1/3/23
to Mike Kaply,

Looks like this was the key. We changed the mime type to "application/redars" and it fixed the download issue. We verified this fix in firefox 102.3.0esr.




Simon Keightley


From: Mike Kaply <>
Sent: Wednesday, December 21, 2022 13:19
To: Keightley (US), Simon Q <>
Subject: [EXTERNAL] Re: [Mozilla Enterprise] File types with non-standard extensions opening


EXT email: be mindful of links/attachments.

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