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Steam.exe (main exception): CMultiFieldBlob(pSerialized)

I'm receiving an error when I try to start Steam with the message "Steam.exe (main exception): CMultiFieldBlob(pSerialized):" followed by a specific reason - how should I fix this?

Solution for Windows

To fix this error use the following steps:

  • Exit Steam
  • Navigate to your Steam installation directory. (C:\Program Files\Steam\ by default.)
  • Delete everything in that directory EXCEPT the following:
    • steam.exe
    • steamapps directory (All of Steam's game files are kept here.)
  • Restart Steam to test the issue

Solution for Mac

To fix this error use the following steps:

  • Exit Steam
  • Navigate to Users/[username]/Library/Application Support/Steam by default.)
  • Delete everything in that directory
  • Launch Steam.app from your Dock or Applications folder

Cause

This error results from a corrupted ClientRegistry.blob file, typically caused by Steam unexpectedly closing. This is often due to a crash or because the Steam.exe process was killed before Steam finished writing to the file.

Some instances of this error can be avoided by allowing Steam to fully exit by clicking Steam ▸ Exit or by right-clicking on the Steam icon in the System tray and clicking Exit, rather than forcing the process to end.

Problem with Steam?

Contact Steam Support
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