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.

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 an external application (exceptions to this are PDF files with a MIME type incorrectly set). This built-in PDF viewer is enabled by default. When you click on a link to a PDF file or open it from the Firefox Downloads panel, it will be rendered with the built-in PDF viewer. To learn more about the built-in PDF viewer, see Using Firefox's built-in PDF viewer (below).

The built-in PDF viewer will open a PDF file in Firefox without saving it. If you want to save the PDF file to your computer, you can use the download button in the PDF viewer's toolbar.

Use a third-party PDF viewer for downloaded PDF files

When Firefox is set as the default PDF viewer, you can still use a different application to view PDF files you downloaded to your computer in Firefox, by following these steps:

1. Open the Downloads panel by clicking the download icon next to the address bar. (Alternatively, open the Downloads Library window.)
2. Right-clickHold down the control key while you click on the download entry for the PDF file you want to open.

   

3. Click on the context menu item for the system default PDF viewer (for example, click on Open in Adobe Acrobat Reader DC) (for example, click on Open in Preview) to open the PDF file in that application.

Note: If you want to open the PDF file in a different viewer, open the Downloads panel or Downloads Library window as explained above but click on the file folder icon for the PDF file entry. This will open the folder containing the downloaded file.click on the magnifying glass icon for the PDF file entry. This will open the folder containing the downloaded file in Finder. You can then right-clickcontrol-click on the file, select Open with and choose your favorite PDF viewer.

Choose another PDF viewer or set Firefox to always ask

Disable the built-in PDF viewer and use another viewer

You can also set a different third-party PDF viewer to handle PDF files, instead of Firefox’s built-in PDF viewer. To switch from using the built-in PDF viewer to another 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.

   

Set Firefox to ask you what to do with PDF files

If you want Firefox to always ask you what to do with PDF files, follow the above steps to change the action for the Portable Document Format (PDF) entry, except select Always ask from the drop-down menu. The next time you click on a link to download a PDF file, Firefox will show you a prompt asking what to do with the file. You can then choose to open it with Firefox's built-in PDF viewer, open it with a different PDF application, or you can choose to save the file.

For more information, see Manage file types and download actions in Firefox.

Using Firefox's built-in PDF viewer

Fill out forms in PDF Viewer

Some PDF files have interactive fields to fill in data (such as on forms). Using Firefox's built-in PDF viewer you can fill out fields such as text, check boxes, and radio buttons. After entering data into these fields you can download the file to have the filled-out version saved to your computer.

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.

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