Laptop screen looks crisp, the external monitor is blurry or suddenly tiny. Dialogs get scrollbars they shouldn't have.

DPI scaling across mixed panels has been a Windows bug source for years. The fix is usually a combo of scaling setting, app compatibility flag, and sometimes a re-login.

Try this first

1. 1Open Settings, System, Display. Click the external screen and set scaling to 100 percent if it's 1920x1080 or 2560x1440. On 4K typically 150 percent. Per-display independent.
2. 2Sign out fully and back in. Many apps read DPI only at start, so switching mid-session stays blurry.
3. 3For specific apps that stay blurry (old Win32, Adobe, Office on some builds): right-click the exe or shortcut, Properties, Compatibility, 'Change high DPI settings', tick 'Override high DPI scaling behavior' with 'Application' or 'System'.
4. 4With multiple monitors at different scale percentages: avoid dragging a window from 100 to 150 percent and back. Windows 11 is better, 10 still buggy. Open the app on the screen where you use it.
5. 5For remote desktop sessions (RDP, Citrix): match host scaling to client or use the client's DPI-aware mode. Otherwise you get double scaling.
6. 6On Mac with Retina plus external display: System Settings, Displays, click external, pick a 'Looks like X' option that fits. Not the panel's native if that's too small.

None of the above fits?

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