Invalid CefExecuteProcess return code of 0

Example Error Messages

This troubleshooting article is for those who are experiencing one of these errors:

  • Cef interface process check returned value 0 !!!
  • Invalid CefExecuteProcess return code of 0
  • Invalid CefExecuteProcess return - code of 0
  • Error (source -1): 'Invalid CefExecuteProcess return code of 0'
  • Interop 'InitializeSync()' result: 0

Possible Causes

  1. CEF, cefSharp.Common or cefSharp.Winforms - or some other CEF-based product is present in the same project.
  2. The runtimes folder, or some required files from this folder are not present.


  1. First, ensure you do not have cefSharp.Common, cefSharp.Winforms, or any CEF-based library installed in your project.
  2. If you previously had a CEF-based library installed, clean up any lingering files. CEF-based libraries can store these files in your project directory and due to name-conflict IronPDF may unintentionally use them.
  3. Ensure you have NO non-IronPDF-related files in your directory that have name conflicts with those in the runtimes folder. Navigate to /runtimes/_/natives/ from this link and ensure none of these files exist elsewhere in your project.