What Is dwm.exe and Why Is It Running?

You are no doubt reading this article because you are wondering why this dwm.exe process is taking more memory than you think it should, and you are curious what it does. Thankfully for you, we have the answer.

This article is part of our ongoing series explaining various processes found in Task Manager, like svchost.exectfmon.exemDNSResponder.exe, conhost.exe, rundll32.exeAdobe_Updater.exe, and many others. Don’t know what those services are? Better start reading!

So What Is It Anyway?

Desktop Window Manager (dwm.exe) is the compositing window manager that gives you all those pretty effects in Windows Vista: Transparent windows, live taskbar thumbnails (that you can resize now), and even the Flip3D switcher that you can disable and replace with Switcher.

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What happens in Vista is that applications write the picture of their window to a specific place in memory, and then Windows creates one “composite” view of all the windows on the screen before sending it to your monitor. Because Vista is keeping track of the contents of each window, it can add effects when layering the windows such as the transparency we’re all used to, as well as the live preview thumbnails.

The benefit to using this approach is that Windows Vista can utilize the hardware acceleration features in your video card to create very smooth animations for minimizing and restoring, and even for the transparent effects.

What about Memory Usage?

If you open up Task Manager, you can see the dwm.exe process in the list, typically taking somewhere between 30-50MB of memory in my testing:

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The size of the DWM process is controlled by the number of windows that you have open, since each window requires a buffer in memory to store the contents of the window. If you have a large number of very large windows open, DWM will use more memory.

The benefits of using a compositing window manager are worth that relatively small amount of memory under most circumstances.

Does Switching to the Vista Basic Theme Turn it Off?

The short answer is no, just switching to the Vista Basic theme will not turn off DWM, but it will reduce the memory usage a great deal.

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How do you switch to Vista Basic? Just right-click on the desktop, choose Personalize, and then Window Color and Appearance:

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Click on classic appearance properties at the bottom:

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Then choose Windows Vista Basic and click the Apply button:

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Note that I’m not recommending switching to the Basic theme, just explaining how to do it.

So How Do I Turn dwm.exe Off Then?

Note that I don’t recommend turning this off unless you are playing games in fullscreen mode, and even then it likely won’t help increase speed.

The only way to get rid of the dwm.exe process is to stop the service from running. Open up Services from Control Panel or the start menu, and then find the “Desktop Window Manager Session Manager” service in the list, and click the stop button. Note that you will be switched to the Vista Basic theme when you click the button.

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To permanently disable it, double click on the item and select Disabled from the “Startup type” drop-down:

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If you want to use the command line instead, you can open an administrator mode command prompt and use one of these commands:

Stop Service net stop uxsms
Start Service net start uxsms
Disable Service sc config uxsms start= disabled
Enable Service sc config uxsms start= auto

By now you should understand what the process does… do you really still want to get rid of it?

Lowell Heddings, better known online as the How-To Geek, spends all his free time bringing you fresh geekery on a daily basis. You can follow him on if you'd like.

  • Published 05/20/08
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