Installer Patch Cache
Windows keeps a local patch cache in %WinDir%\Installer\$PatchCache$ containing baseline and transformed .msp and related Windows Installer patch files so MSI can repair, modify, or uninstall patched products without always prompting for original media. Over time this cache accumulates superseded patch payloads and orphaned installer data left behind by updates and application removals, consuming space even though the active product state is already registered elsewhere in Windows Installer metadata. Kudu removes removable, stale patch-cache content from this protected system location while leaving installed applications, user files, accounts, passwords, and current Windows Installer registration intact.
Why clean Installer Patch Cache?
- Superseded .msp patch payloads remain in $PatchCache$ after newer updates replace them, and users usually notice only that the Windows folder keeps growing with no obvious large files in normal app folders
- Orphaned patch cache entries from software that was already removed leave behind installer data, showing up as unexplained disk usage on the system drive long after the program is gone
- Damaged cached patch files can make Windows Installer repeatedly ask for source media during repair or uninstall, even though the application itself still launches normally
- When the patch cache contains stale or partially missing baselines, maintenance operations such as Modify, Repair, or Uninstall can fail with Windows Installer errors instead of completing cleanly
- Large accumulations under %WinDir%\Installer\$PatchCache$ reduce free space needed for feature updates and application servicing, which users notice as update failures or low-disk warnings on C:
- Because this cache sits in a protected Windows directory, manual cleanup is error-prone and often leaves users with access denied messages unless the removal is done with administrative privileges
Cache paths Kudu targets
Windows
%WinDir%/Installer/$PatchCache$ |
Common questions about Installer Patch Cache
Download Kudu and reclaim your disk space.
Available on Windows, macOS, and Linux. No account required, no feature gates, no telemetry without consent. All cleaning targets are open source and community-auditable.