I'm on Windows 11 home. I use Firefox for my browser. I want PDFs that are on my PC to open in an app on my PC. I want PDFs that are online to open in my browser without downloading to my computer. I only want to view a PDF online, not keep it. Is there a way to do that?

  • 2
    All the PDFs I view (numerous) are downloaded first.
    – John
    Dec 23, 2023 at 19:33
  • 1
    “I only want to view a PDF online” - The way you do that is download the PDF then open the file using whichever application you want to use.
    – Ramhound
    Dec 23, 2023 at 20:38
  • 1
    Sometimes, the PDF file is just shown, like an HTML page or an image file. Sometimes it is downloaded to a non-temporary location and then opened from there. This is probably what OP is referring to.
    – Daniel B
    Dec 23, 2023 at 21:25

4 Answers 4


See the Mozilla article View PDF files in Firefox or choose another viewer.

It describes enabling the PDF viewer that is built-in into Firefox:

You need to Manage file types and download actions in Firefox and set "Portable Document Format (PDF)" files to "Open in Firefox". As this option is the default option for PDF in Firefox, this should already be the case for you, unless it was changed.

Note that it's impossible for Firefox to create the viewable text you see without having the PDF file entirely downloaded to a temporary location. The temporary file is removed when you close the tab used by the PDF viewer.

  • Open about:config in the address bar
  • Search for browser.download.open_pdf_attachments_inline and set it to true
  • Go to SettingsGeneralFiles and ApplicationsApplications
  • Look for Portable Document Format (PDF) (application/pdf) and set it to Open in Firefox

For more details, see:


If PDF files are "ONLINE" then they can be converted "online" into safer downloadable HTML and images.

EVERY thing you see "online" is downloaded to your device and actually you are always viewing the offline reproductions. Disconnect your internet and the page contents are still visible because they are in the device.

Thus using an "online" viewer a PDF cannot exploit your browser as you are insulated from the PDF internal code.

There are several methods.

One is to use a PDF.js middleware worker and actually Firefox PDF Viewer uses something along those lines.

Another is to use Google Microsoft or others cloud services to open the file and show you via download a reproduction.

So here is an example of filtering via google. https://docs.google.com/gview?url=https://github.com/GitHubRulesOK/MyNotes/raw/master/colours.pdf&embedded=true Here we see it is an image not the true PDF content enter image description here

Another using Word for DocX in a similar fashion https://view.officeapps.live.com/op/view.aspx?src=https%3A%2F%2Fpdftron.s3.amazonaws.com%2Fdownloads%2Fpl%2FQuote_.Word.docx&wdOrigin=BROWSELINK


The only way would be to upload the PDF to Google Drive or Dropbox, or share the link to the pdf and then open it in Google Drive or Dropbox. Apart from Google Drive and Dropbox, another option is using PDF viewer websites. Websites like "SmallPDF" and "PDF Online Viewer" allow you to view PDFs online without downloading them

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