Firefox includes a built-in PDF viewer to display PDF files inside the browser window. This article explains how to use the built-in PDF viewer, how to fix the common issues you might encounter, and how to use another PDF viewer.

Use Firefox’s built-in PDF Viewer

Firefox includes a built-in PDF viewer that allows you to view almost all PDF files found on the web without a plugin. Exceptions to this are PDF files with a MIME type incorrectly set. This built-in PDF viewer is enabled by default.

Downloaded PDF file will be rendered with the built-in pdf viewer when you click on one in them from the Downloads panel.

PDF Viewer toolbar functions

• View document thumbnails or outline - The slider button on the far left will open a sidebar with thumbnails of the document's pages. Some documents will also have an outline view available. These make it easy to navigate through a long document.

  

• Page up and down or skip directly to a page - You can use the up and down arrows to page through a document or enter the number of the page you want to go to.

  

• Change the size of the document - Use the + and - buttons to zoom in and out or choose a zoom setting from the dropdown menu.

  

• Fullscreen or Presentation mode - Click the fullscreen button to allow the PDF file to take over your entire screen. Press ESC to exit fullscreen mode.

  

• Print - Click the Printer button to open the print setup dialog.

  

• Download - Click the Download button to save the PDF file to your computer or to open it with a PDF reader program.

  

• Copy current view - Right-clickHold down the control key while you click the current view button to open the current view in another tab or window.

  

PDF Viewer keyboard shortcuts

Troubleshoot problems with the PDF viewer

• With certain types of PDF files, the PDF Viewer may have problems displaying fonts, colors or the whole document. If some PDF files don't render well or are blank, click the download button on the right side of the document header to open it with the default PDF viewer application on your computer.

• If you can't open any PDF files with the built-in PDF viewer, a Firefox extension could be the cause. You can disable all of your extensions, to see if one of them was the problem. For details, see Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems.

Disable the built-in PDF viewer and use another viewer

You can also use a different third party PDF viewer instead of Firefox’s built-in PDF viewer. To change from using the built-in PDF viewer to another PDF viewer:

1. In the Menu bar at the top of the screen, click Firefox and then select Preferences or Settings, depending on your macOS version.Click the menu button and select Settings.
2. In the General panel, go down to the Applications section.
3. Find Portable Document Format (PDF) in the list and click on the entry to select it.
4. Click on the arrow under the Action column for the above entry and select the PDF viewer you wish to use from the drop-down menu.

Use a third party PDF viewer for downloaded PDF files

You can choose to have Firefox’s built-in PDF viewer as the default for viewing PDFs in the browser but open downloaded PDFs with a third party tool. To open a downloaded PDF with a third party viewer:

1. Open the the Downloads panel by clicking the download icon next to the address bar.
2. Right-click on the file folder icon of the PDF file and select Open Containing Folder.Hold down the control key while you click (two finger click) the magnifying glass icon of the PDF file and select Show in Finder.
3. Then in the Downloads folder, right-clickControl-click on the file and select Open with and choose your favorite PDF viewer.