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Why does the /winsxs folder grow so large, and can it be made smaller?

I want to free some space from C drive... when I checked which folder holding more from Tree size Free tool, I found following location is holding more data? Is it safe to delete those folders?


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marked as duplicate by Tom Wijsman, Indrek, 8088, Renan, Nifle Sep 6 '12 at 2:37

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Keep in mind that every DLL somewhere in your Windows directory is merely another hardlink to a file also contained within WinSxS. That greatly skews perception of size for that folder as this doubles the perception of your Windows folder's size but not the actual contents on disk. I doubt your tool will account for that. – Joey Oct 15 '09 at 15:08
up vote 10 down vote accepted


The winsxs folder is used for keeping previous versions of files that are replaced during setups. For example, in previous versions of Windows, if you installed an application that required changing abc.dll, it would just do it. In Windows Vista and 7 it will keep a copy of the original and changed abc.dll and keep a version in winsxs so that each application can keep its own version.

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Note that he might also want to delete the System32 directory, which contains every important DLL and application for Windows and would be a huge no-no as well. You may want to stick this in your answer too. – Will Eddins Oct 15 '09 at 15:45
+1. My exact thought, and my exact answer when i read the question title, was No!. It's important to note that WinSxS should not be thought of as a "backup". WinSxS is a mechanism where multiple versions of a DLL are maintained, so that programs that depend on a specific version are able to access that version. Deleting alternate versions of DLLs would be a bad thing. – Ian Boyd Mar 2 '11 at 15:08

You shouldn't mess with the contents of winsxs under any circumstances.

See this blog post to get an understanding of what it's for.

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Don't delete system32 - it's essential to the operation of Windows. This page sums it up nicely.

Basically, System32 is a directory that is required on any Microsoft Windows system. So, if you use Windows, you've got to have System32 working in order for your computer to run properly.

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Generally speaking, you shouldn't mess with anything inside the Windows folder unless you really know what you're doing.

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You can get a 500 GB hard drive for fifty bucks US on sale. Add storage--hardware is super-cheap these days and it's really dangerous to screw around with the Windows folder.

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i love how the word "dangerous" is used in these contexts ... - like it's gonna blow ... - you mess with it, you screw up, you reinstall ... a few hours wasted ... but hardly "dangerous" – Rook Oct 15 '09 at 15:22
@idigas it's "dangerous" to people who don't backup their systems, and don't know what to do when Windows stops working. – Tester101 Oct 15 '09 at 15:52
well, to them the delete option on right mouse click is equally dangerous ? One cannot not be responsible for one's own actions. – Rook Oct 18 '09 at 0:45

Do not manually delete any winsxs contents. However you can use cleanup tool which will remove stuff no longer needed if you don't intend to uninstall SP1 or SP2.

  • If you already have SP2 use Vista SP2 Service Pack Clean-up tool (Compcln.exe).
  • If you only have SP1 use Vista SP1 Clean-up tool (Vsp1cln.exe)
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Do not delete this folder is for dll copies

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The answer seems to be "no"!

You'd be better off using clean up tools like ccleaner, eusing or glaryutilities. And get an external drive for when your machine gets full and for back ups.

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