Skip to contentGo to the directory tree
Windows Directory Tree
  1. C:
  2. Windows
  3. Logs
  4. MoSetup
FolderRisk: Caution

MoSetup C:\Windows\Logs\MoSetup

Logs of Modern Setup for Windows 10 and 11 upgrades, including BlueBox.log and UpdateAgent.log, read by SetupDiag.

Updated on By AltF4 Formation

What it’s for

MoSetup (Modern Setup) installs Windows 10 and 11 feature updates and upgrades from Windows Update. This folder keeps its logs. BlueBox.log and UpdateAgent.log in particular are read by SetupDiag, Microsoft’s upgrade diagnostic tool.

What it contains

  • UpdateAgent.log: actions of the update agent during the upgrade.
  • BlueBox.log, the other file SetupDiag reads.
  • These logs complement those in Panther and $WINDOWS.~BT.

Risks and best practices

  • Deleting these files does not hurt Windows, but it erases the evidence of a failed upgrade. Keep them until the upgrade is validated.
  • After a failure, hand them to SetupDiag or to support.
  • They may cite machine names and paths, so review them before sharing.

Useful commands

Fenêtre de terminal
# Errors and 0x codes in the MoSetup logs
Select-String -Path "$env:windir\Logs\MoSetup\*.log" -Pattern 'error|failed|0x[0-9a-f]{8}' | Select-Object -Last 30


# Last lines of UpdateAgent.log
Get-Content "$env:windir\Logs\MoSetup\UpdateAgent.log" -Tail 50 -ErrorAction SilentlyContinue

Report a mistake