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Why do some PDFs open in Firefox but others need to be opened with Acrobat?

Icarium
Icarium
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Firefox seems to open most PDFs directly but some it wants to open using an external program. Is there some limitation of PDF versions or content?

Firefox seems to open most PDFs directly but some it wants to open using an external program. Is there some limitation of PDF versions or content?

All Replies (1)

jscher2000 - Support Volunteer
jscher2000 - Support Volunteer
  • Top 25 Contributor
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If Firefox does not even try to load the file, the server might have sent it with a non-standard header. Two scenarios:

(1) Normally, a server will send the content-type "application/pdf" ahead of the file. If the server sends a different content-type, then Firefox will not handle it as a PDF.

(2) Normally, a server does not specify whether content can be viewed in the browser or must be saved. If the server send a header indicating that the content-disposition is "attachment" then Firefox will always display the download dialog. (There is an add-on you can use to work around this if you like: https://addons.mozilla.org/firefox/ad.../inlinedisposition/)