How to help us debug Sumatra hangs or crashes

If Sumatra crashes or hangs reliably on your machine but we can't reproduce it ourselves, you can help us by debugging it. Here's a tutorial on how to do it.

Please first test with latest pre-release version from

Some bugs might already be fixed there compared to latest

Those instructions require SumatraPDF 3.2 or later.

Install necessary software

First, vocabulary. %ProgramFiles% means the standard directory where Windows installs programs. It's c:\\Program Files on 32-bit Windows and c:\\Program Files (x86) on 64-bit Windows.

Debugging a crash

To debug crashes:

Debugging a hang

Here are the steps to follow if Sumatra hangs

  1. Start SumatraPDF.exe and get it to hang
  2. start WinDBG.exe
  3. use File/Attach to process (F6) and select SumatraPDF.exe from the
  4. In WinDBG, type: