Quick fix: CoreWindow.exe handles UWP app windows. Long display sleep periods can leave its working set holding references to objects that should be released. Restart Explorer (which also restarts CoreWindow) via Task Manager, or call (Get-Process -Name CoreWindow).Refresh() in PowerShell to trigger garbage collection.
You leave the PC running but with display off for several hours. On wake, CoreWindow.exe has accumulated 500+ MB of memory. Closing UWP apps doesn’t release it. The process keeps growing across sleep/wake cycles.
Affects: Windows 11 with many UWP apps.
Fix time: 5 minutes.
What CoreWindow.exe does
CoreWindow is the rendering host for UWP (modern) app windows. Each UWP app communicates with CoreWindow for window management, input, and composition. The process maintains object references for every active UWP window plus some caching for recently-closed ones.
Method 1: Restart Explorer to clear CoreWindow state
- Task Manager → Details tab → find explorer.exe.
- Right-click → End task.
- File → Run new task → type
explorer.exe→ OK. - CoreWindow restarts with Explorer. Memory returns to baseline.
Method 2: Limit UWP apps that stay resident
- Settings → Apps → Installed apps. For each UWP app you don’t actively use:
- Click three-dot menu → Advanced options.
- Under Background apps permissions, set to Never.
- The app stops running when closed, reducing CoreWindow refs.
Method 3: Schedule periodic Explorer restart
- Create a scheduled task that runs daily during inactive hours:
taskkill /f /im explorer.exe && start explorer.exe - Memory baseline maintained across days.
Verification
- Task Manager → CoreWindow.exe memory drops to ~50–100 MB after Explorer restart.
- Sleep/wake cycle no longer accumulates memory in CoreWindow.
If none of these work
For chronic memory growth, the cause may be a specific UWP app holding references. Use Process Explorer to check open handles per UWP process; close offenders. Some Microsoft apps (Photos, Mail) historically had CoreWindow-related leaks — ensure they’re on latest version.
Bottom line: CoreWindow leak = UWP window state accumulation across sleeps. Restart Explorer to clear; disable background apps to prevent.