Rounded Corners Not Working in Windows 11? How to Check and Fix Square Corners

If your Windows 11 windows have square corners, first double-click the window’s title bar to restore it, because maximized and snapped windows are square by design. If every restored window is still square, check your graphics driver in Device Manager.

Microsoft’s other documented exceptions include some custom app frames and virtual machines or Azure Virtual Desktop sessions, and the quick check below rules those out before you change settings. The visual change from Windows 10 or a question about a Remote Desktop session does not establish a cause on your PC.

Quick Checks and By-Design Exceptions

Windows 11 applies system-rounded corners to its built-in apps and most other top-level app windows. Some customized Win32 windows are exceptions. Windows also keeps corners square by design in some situations, so check these before you change anything:

If every restored window is still square, work through the fixes below in order.

Microsoft documents the by-design cases in the quick check and FAQ, but it doesn’t document a specific cause for square corners on an ordinary restored window. The steps below are low-risk checks ordered from quickest to most time-consuming, not by how likely each is to be the cause, and none is a guaranteed fix.

Troubleshooting Fixes for Windows 11 Rounded Corners Not Working

Rounded corners are drawn by Desktop Window Manager (DWM). Microsoft doesn’t document a graphics-driver problem as a cause of square corners on ordinary restored windows, so treat this as an editorial troubleshooting step: if the corners changed right after a driver or Windows update, checking which display driver is loaded is quick and low-risk.

In one Microsoft Q&A thread on missing round corners (retrieved 2026-10-20), square corners inside a VMware virtual machine came back after the poster rolled back a VMware update, which points to the virtual display driver in that one case; it doesn’t prove the same cause on a physical PC.

If Windows can’t find a driver, laptop and prebuilt-PC owners should start with the PC maker’s support page, because many of those systems use a customized driver package and a generic driver (especially a clean install) can remove maker-specific components. On a desktop with a separate graphics card, download the latest driver from NVIDIA, AMD, or Intel.

Verify it worked: Restore a window and check the corners after the restart. If they’re still square, move on to the next check. One test doesn’t fully rule the driver out, but further driver changes are unlikely to be worth the effort.

Tip: A yellow warning icon on the adapter with “Windows has stopped this device because it has reported problems. (Code 43)” can mean a driver problem or a failing graphics card. Code 43 alone doesn’t prove the hardware is failing. Try reinstalling the driver from your PC or card maker first. If the error persists, contact the PC maker’s support, or on a desktop with a separate card, have the card tested before deciding whether a graphics card upgrade makes sense.

Microsoft’s rounded corners documentation doesn’t list Transparency effects, Animation effects, or the Adjust for best performance preset as controls for window rounding (checked October 20, 2026). Treat this as a quick, reversible check rather than a known fix, and only bother if the corners went square around the same time you changed these settings.

Verify it worked: Open File Explorer, restore it to a normal size, and check the corners. If they’re still square, these settings probably aren’t the issue; set them however you like and move on.

If you want to start a fresh local session, use Windows’ normal sign-out action. This is a general session check, not a documented cure for square corners or proof that DWM failed. We don’t give a way to restart DWM directly because Microsoft doesn’t document a supported method for ordinary users; signing out (or restarting) is the safe way to get a fresh desktop session. Microsoft’s sign-out guidance warns that open apps close and unsaved work may be lost.

Warning: Don’t try to “restart” Desktop Window Manager by ending it in Task Manager. It’s a protected Windows process, and ending it isn’t a supported restart method; it can leave you with a black screen. The screenshot below shows the Task Manager End task option on Desktop Window Manager so you can recognize it and avoid it; it is not a step to perform.

Verify: If the corners are rounded again, the fresh session helped, though that doesn’t show what caused the problem. If they’re still square, this reset simply didn’t help; continue with the next fix.

If you connected to this PC remotely and the corners are square when you sit down at it, a full sign-out starts a fresh local session. We haven’t found Microsoft documentation linking Remote Desktop to square corners on the local session, so treat this purely as a quick test.

Verify: Check a restored window after you sign back in. If the corners are still square, this reset didn’t help; that doesn’t rule Remote Desktop in or out, so continue with the next fix.

If nothing else worked, rule out pending updates and system file corruption. This is general Windows maintenance rather than a documented fix for corners. It needs administrator access, and the scans can take a while, so keep the PC plugged in until they finish.

Verify it worked: Restore a window after the restart. For more detail on reading the scan results, see our guide to fixing corrupted files with SFC and DISM in Windows 11.

FAQ and Summary of Causes

Some people prefer square corners. Before you troubleshoot, check that nobody else who uses this PC made that change on purpose.

We couldn’t find an option in Settings or a Microsoft-documented way to turn off rounded corners for all windows; Microsoft’s rounded corners documentation covers only a preference that app developers set for their own windows. Your options are limited:

If none of these trade-offs suit you, maximizing or snapping windows gives you square corners with zero risk.

If the corners still won’t come back, gather this information before you post on Microsoft Q&A or contact your PC maker:

Developers can tell Windows not to round their app’s windows using a setting called DWMWCP_DONOTROUND, as described in Microsoft’s rounded corners documentation (retrieved 2026-10-04). The same page explains that apps with heavily customized window frames may not be rounded automatically, and apps that use per-pixel alpha layering or window regions can’t be rounded at all. Updating the app may help, but you can’t change this from Windows settings.

Microsoft’s rounded-corners documentation lists virtual machines, Azure Virtual Desktop sessions, and Windows Defender Application Guard windows as cases that are not rounded by design. It does not establish missing GPU acceleration as the cause or recommend extra video memory as a corner-rounding fix. Do not change those resources solely to make corners round.

Most square corners turn out to be by design, so restore the window and check other apps before changing anything. If you also see Code 43, screen artifacts, or random black screens, treat that as a graphics driver or hardware problem worth fixing in its own right.

Last updated: October 20, 2026 | Applies to Windows 11 Rounded Window Corners (Desktop Window Manager) on Windows 11

Summary table of common troubleshooting scenarios:

System status messages and actions:

Action steps overview:

Addressing rounded corners not working in Windows 11 involves verifying normal window states, updating graphics drivers, checking system settings, and reviewing system files.