Adobe has a whole set of procedures to troubleshoot the start up of Lightroom. One of their recommendations is:

  • Re-create the Photoshop Lightroom preferences file

Then Adobe says:

If the problem continues, the preferences file isn’t the cause.

How to recreate the Lightroom preferences file

  1. Exit Lightroom.
  2. Rename the Lightroom Preferences.agprefs file. I always rename to .original so the preferences file would be renamed to: preferences.agprefs.original

    • For Windows XP, the preferences file is located in: Documents and Settings\[username]\Application Data\Adobe\Lightroom\Preferences\.
    • For Windows Vista, the preferences file is located in: Users\[username]\AppData\Roaming\Adobe\Lightroom\Preferences\
    • For OSx, the preferences file is located in: [username]/Library/Preferences/com.adobe.Lightroom.plist
    • Then restart Lightroom and Lightroom will create a brand new preferences file.
  • [username]: Your own user name that you signed in

Why recreate the Lightroom preferences file

Adobe asks you to recreate the preferences files, in case it is corrupted. That’s the official version. But the likelihood that the preferences file becomes corrupted is very minimal. If that happened, you would also corrupt the database and many of the photos. Corruptions don’t happen that easily.

The main problem with the preferences is that there are so many of them, many users set them wily-nily, then Lightroom does not behave “properly” anymore. So the simplest method is to wipe it out and start fresh.

To restore your settings:

  1. Exit Lightroom.
  2. Delete the new preferences file .
  3. Restore the original name of the previous preferences file.
  4. Restart Lightroom.

What’s the preferences.agprefs file

It’s a simple text file that is read when you start Lightroom. The settings are saved when you exit Lightroom. Here is part of my preferences.agprefs file”

    prefs = {
        Adobe_checkCatalogIntegrityForPaths = "catalogsToCheck = {\
    }\
    ",
        Adobe_pendingBackupPaths = "pendingBackups = {\
    }\
    ",
        Adobe_pendingVacuumPaths = "pendingVacuum = {\
    }\
    ",
        AgApplication_HasRegisteredAutoPlay = true,
        AgBatchConvertToDNG_deleteOriginalNegative = false,
        AgBatchConvertToDNG_onlyConvertRAW = true,
        AgCameraRawNamedSettings_autoGrayMixer = false,
        AgCameraRawNamedSettings_autoTone = false,
        AgCameraRawNamedSettings_brightness = true,

    ........... CUT ................

        whichRightPanel = "adjust",
        whiteBalanceShowLoupe = true,
        whiteBalanceToolSticky = false,
        xmpTreatBackSlashAsSeparator = false,
        xmpTreatDotAsSeparator = true,
        xmpTreatForwardSlashAsSeparator = true,
    }

I am showing only a small portion of the preferences files:

  1. My Lightroom preferences file is 873 lines.
  2. Each Lightroom preferences file is customized to your computer and your usage. The Lightroom preferences file stores the last screen position, the last catalog, the last image, the last image preview size, each of your preference, each of the last usage of the various tools…