Are you using Firefox for Android? You are posting in the forum for help with Firefox for Android. The user agent you are using to access this forum says that you are using Chrome on iOS.

kbrosnan said

Are you using Firefox for Android? You are posting in the forum for help with Firefox for Android. The user agent you are using to access this forum says that you are using Chrome on iOS.

No. I am using Firefox on windows 8.

Moving to desktop.

I don't have a specific solution. Checking if any of the troubleshooting options help https://support.mozilla.org/en-US/kb/troubleshoot-and-diagnose-firefox-problems

Hi dalun, does this problem only occur with PDFs embedded into other pages, or also PDFs that load in their own tab, such as:

https://www.jeffersonscher.com/temp/userChrome_css.pdf

In case Firefox can't load a PDF in its own tab, could you try switching it between Always Ask, Save File, and Preview in Firefox? Please close the Options page and re-open it in between changes.

jscher2000 said

Hi dalun, does this problem only occur with PDFs embedded into other pages, or also PDFs that load in their own tab, such as: https://www.jeffersonscher.com/temp/userChrome_css.pdf In case Firefox can't load a PDF in its own tab, could you try switching it between Always Ask, Save File, and Preview in Firefox? Please close the Options page and re-open it in between changes.

The problem only occurs while opening embedded PDFs.

It's probably the way the page is designed. It may be checking for a PDF plugin and displaying the message if it doesn't find one. Can you give a link to an example page where this happens?

The builtin Firefox PDF viewer only works for files send by the server as application/pdf.

cor-el said

The builtin Firefox PDF viewer only works for files send by the server as application/pdf.

Oh! I see. Thank you!