How to Open PDF Files in SumatraPDF in Firefox

All the modern web browsers come with an in-built PDF viewer which comes very handy when you have to quickly view and read through a PDF file available on the internet. But for some people the browser’s PDF viewer is slow and does not have the features that they are familiar with.

For example, I am very fond of the SumatraPDF PDF viewer application as it is very lightweight and renders all the pages in a PDF file in just a fraction of a second.  It does not matter how big the PDF file is, SumatraPDF can open and show it in seconds. Navigation is also very fast when you are using SumatraPDF.

So if you want to enable opening all the PDF files or links to the PDF files in Firefox web browsing using the SumatraPDF PDF viewer, then you can follow these steps:

  1. First of all you have to download and install SumatraPDF from
  2. After installation of SumatraPDF, open any PDF file and choose SumatraPDF as the PDF application to be always used to open PDF files.Use SumatraPDF as PDF Viewer in Firefox
  3. Launch Firefox and enter about:preferences in its address bar.
  4. In the Preferences window, select the General category and scroll down until you found the Files and Applications section.
  5. Find Portable Document Format (PDF) and choose Use Windows Default Application as its Action.Use SumatraPDF as PDF Viewer in Firefox
  6. Restart Firefox and you are all done.

Now if you click on a PDF link in Firefox, it will be downloaded and then opened in SumatraPDF. If you have configured Firefox to ask for download location then you will be asked for the download folder first and then it will launch SumatraPDF to open the downloaded PDF file. The same process can be used if you are using a portable copy of SumatraPDF PDF viewer but in that case you have manually pick the SumatraPDF EXE file in the Firefox settings.