Is It Safe to Delete Windows.old and "Temporary Files"? ── When to Use Storage Sense and When to Use Disk Cleanup

When the C drive runs low on space, Windows Settings shows large entries such as “Temporary files” and “Previous Windows installation(s)”. In File Explorer you will also find a large folder named Windows.old.

Here is the answer first.

• Windows.old: If you don’t need to go back to the previous Windows, you can delete it. But once deleted, you cannot go back. It is deleted automatically 10 days after the upgrade. Depending on how the upgrade was done, your own files may still be in it, so check the Users folder inside before deleting.
• Items under “Temporary files”: Most are working files created by Windows. However, Downloads and the Recycle Bin contain your own files, so look at what is in them before deleting.
• WinSxS and the page file: Microsoft warns that WinSxS must not be deleted by hand. The page file is also used for Windows to run, so it is not something to delete to free up space.

The test is “Is there anything I can no longer get back after deleting it?” This article is for people using Windows 11 and Windows 10, and is based on Microsoft documentation checked on November 3, 2026. The names on the Windows 11 screens were checked on a virtual machine running Windows 11 Enterprise evaluation (26H2). However, because that Windows was freshly installed, it had no Windows.old, and deleting Windows.old was not tried. The Windows 10 screens were not checked either. Check the screen names and defaults on your own version of Windows.

Whether to Delete Something Depends on “What You Can’t Get Back”

The large files on the C drive fall into three groups by why they are there: files Windows created temporarily for its work, files you saved yourself, and files Windows uses to run.

The first group is what Microsoft’s documentation says can be deleted. Deleting the second group means losing your own files. Deleting the third group by hand can stop Windows from working correctly.

flowchart TB
        accTitle: Sorting the large files on the C drive into three groups
        accDescr: Sorts the large files on the C drive into files Windows created for its work, files you saved yourself, and files Windows uses to run, and shows the effect of deleting each.
        A["Large files on the C drive"] --> B["Created by Windows for its work"]
        A --> C["Saved by you"]
        A --> D["Used by Windows to run"]
        B --> B1["Can be deleted (the docs say so)"]
        C --> C1["Can't be restored once deleted (check the contents)"]
        D --> D1["Don't delete by hand (use the dedicated method)"]

Figure 1: Whether a file can be deleted depends on who put it there and why.

Windows.old is a bit special. Windows created it, but deleting it removes the option to “go back to the previous Windows”. Depending on how the upgrade was done, it may also contain your own files. The next section looks at it in detail.

In the diagram a solid line marks a relation that always holds and a dashed line marks a conditional one (the conditions are given per relation on the detail page). The full list of relations (7 in total, with evidence and certainty) and the definitions of the main concepts are collected on the knowledge map detail page (in Japanese). Data: JSON-LD / Turtle

What Is Windows.old?

Windows.old is the folder that holds the previous version of Windows when you upgrade Windows to a new version¹. It is used to go back to the previous Windows if problems appear after the upgrade.

The period during which you can go back to the previous Windows is limited. Microsoft’s support article explains that in most cases you can go back only within 10 days of the upgrade². After 10 days, the previous version of Windows is automatically removed from the PC³.

Going back also has these conditions².

• Keep the contents of the windows.old and $windows.~bt folders after the upgrade
• Remove any user accounts added after the upgrade
• If you used a USB drive for the upgrade, have that USB drive available

flowchart TB
        accTitle: From the creation of Windows.old to its removal
        accDescr: Shows that an upgrade creates Windows.old, that within 10 days you can go back to the previous Windows, that after 10 days it is deleted automatically, and that deleting it yourself in between means you can no longer go back.
        A["Upgrade to a new version"] --> B["Windows.old is created"]
        B --> C{"Within 10 days of the upgrade?"}
        C -->|"Yes"| D["You can go back to the previous Windows"]
        C -->|"No"| E["The previous Windows is deleted automatically"]
        B -.-> F["Deleting it yourself ends the option to go back"]

Figure 2: Windows.old exists to go back to the previous Windows, and it disappears automatically after 10 days.

If you want to free up space without waiting 10 days, you can delete it yourself once you have confirmed that your files and settings work correctly on the new Windows³. After deleting it, however, you cannot go back to the previous Windows. Microsoft also states that this operation cannot be undone³.

Your Own Files May Still Be Inside

Windows.old may contain not only system files but also your own files. If you choose “Nothing” in “Choose what to keep” during the upgrade, personal files are not moved to the new Windows. The personal files that were not moved are kept in the Windows.old folder for only 10 days⁴. If you delete Windows.old at that point, those files are deleted along with it. Even if you have no intention of going back to the previous Windows, check the contents first.

Microsoft describes how to retrieve them as follows⁴. Because you open other users’ folders, you need administrator rights.

1. Sign in with an account that has administrator rights
2. In File Explorer, open the Windows.old folder on the C: drive
3. Open the Users folder, then the folder with your user name
4. Open the folders that contain the files you need, such as Documents, Pictures or Desktop, and copy the files to another location

How to Delete Windows.old

Microsoft describes using the Settings app as the easiest way to delete Windows.old¹. This operation requires administrator rights³.

On Windows 11¹

1. Open “Settings”
2. Select “System” → “Storage”
3. Select “Cleanup recommendations”
4. Check “Previous Windows installation(s)”
5. Select the “Clean up” button that shows the file size

On Windows 10¹

1. Open “Settings” → “System” → “Storage”
2. Under Storage Sense, select “Change how we free up space automatically”
3. Under “Free up space now”, check “Delete previous version of Windows”
4. Select “Clean now”

The item names follow Microsoft’s support article. If your version of Windows shows different names, look for the items corresponding to “Previous Windows installation(s)” (Windows 11) or “Delete previous version of Windows” (Windows 10) in the English article¹.

flowchart TB
        accTitle: Where to delete Windows.old
        accDescr: Shows that from System, Storage in Settings you select Previous Windows installation(s) in Cleanup recommendations on Windows 11, and Delete previous version of Windows under Change how we free up space automatically on Windows 10.
        A["Settings → System → Storage"] --> B{"Windows version"}
        B -->|"Windows 11"| C["Cleanup recommendations"]
        B -->|"Windows 10"| D["Change how we free up space automatically"]
        C --> E["Previous Windows installation(s)"]
        D --> F["Delete previous version of Windows"]

Figure 3: On either version, Windows.old is deleted from “Storage” in Settings.

What Is in “Temporary Files” Differs by Item

When you open “Storage” in Settings, “Temporary files” contains a number of items. They are all called “temporary files”, but each item holds something different. The table below lists the main items and whether they contain your own files. The item names can differ between Windows versions.

The contents of the table are based on the following sources.

Windows Update Cleanup: This item removes old components replaced by updates and makes the component store called WinSxS smaller⁵. WinSxS is explained in detail in a later section.

Delivery Optimization Files: Delivery Optimization is the mechanism used for Windows Update downloads and similar downloads. This item is its temporary storage area (cache), and on the English Disk Cleanup screen it is named “Delivery Optimization Files”⁶. Microsoft explains that Windows deletes the Delivery Optimization cache automatically. Files are removed after a short period or when they use too much space. If you need the space, Microsoft says you can also delete them manually⁶.

Recycle Bin: Deleted files keep using space until you empty the Recycle Bin⁷. Once it is emptied, they can no longer be restored from the Recycle Bin.

Downloads: Microsoft writes that the Videos, Music, Pictures and Downloads folders often contain large files you saved yourself⁷. You may also have installers or documents you received that you never moved elsewhere. Open the folder and check its contents before checking the box.

Previous Windows installation(s): This is the Windows.old described in the previous section. It appears as deletable system files only after an upgrade within the last 10 days⁷.

flowchart TB
        accTitle: Deciding whether a temporary files item can be deleted
        accDescr: Shows that for each temporary files item, items used by Windows for its work can be deleted as they are, your own files need their contents checked, and the previous Windows needs you to confirm you have no plan to go back.
        A["An item under Temporary files"] --> B{"Who created the files?"}
        B -->|"Windows, for its work"| C["Windows Update Cleanup / Delivery Optimization Files"]
        B -->|"Your own files"| D["Downloads / Recycle Bin"]
        B -->|"The previous Windows"| E["Previous Windows installation(s)"]
        C --> C1["Can be deleted"]
        D --> D1["Open and check the contents first"]
        E --> E1["Decide first that you won't go back"]

Figure 4: Even on the same “Temporary files” screen, Downloads and the Recycle Bin contain your own files.

What Does Storage Sense Delete Automatically?

Storage Sense is a Windows feature that automatically cleans up unneeded files on the C drive. It frees up space by deleting things such as temporary files and the contents of the Recycle Bin⁷. It works only on the system drive where Windows is installed (usually the C drive)⁸.

According to Microsoft’s documentation, Storage Sense is off by default. However, when space runs low, Windows may turn it on, clean up some temporary files, and notify you⁸. On the virtual machine used for checking, it was on right after installation even though there was plenty of free space. Check the state of your own PC on the settings screen. When it is on, you can choose how often it runs. It runs automatically only when you have been signed in and online for 10 minutes or more⁸.

What it cleans up is decided item by item on the settings screen.

Temporary files: Deletes temporary files that are not in use. According to the description of the management policy, temporary files are deleted if the policy is not configured⁹.

Recycle Bin: The setting “Delete files in my recycle bin if they have been there for over” sets the number of days since a file entered the Recycle Bin¹⁰. According to the description of the management policy, if it is not configured, files that have been in the Recycle Bin for more than 30 days are deleted⁹.

Downloads folder: The setting “Delete files in my Downloads folder if they haven’t been opened for more than” sets the number of days a file has not been opened¹⁰. According to the description of the management policy, if it is not configured, files in the Downloads folder are not deleted⁹. If you specify a number of days, files not opened for that many days or longer are deleted.

Cloud content: This setting makes OneDrive and other cloud files online-only again if they are not opened for a while. The screen says the “content will become online-only”¹⁰. Microsoft’s support article states that this setting does not permanently delete files. Files you marked “Always keep on this device” are excluded⁸.

flowchart TB
        accTitle: What Storage Sense deletes
        accDescr: Shows that Storage Sense targets temporary files, the Recycle Bin and files in the Downloads folder on the system drive, and that it deletes files in the Downloads folder only when a number of days is set.
        A["Storage Sense (system drive only)"] --> B["Temporary files"]
        A --> C["Recycle Bin"]
        A --> D["Downloads folder"]
        B --> B1["Deletes ones not in use"]
        C --> C1["Deletes after the set number of days"]
        D --> D1["Deletes only when a number of days is set"]

Figure 5: Storage Sense behaves differently for each item, and deletes from the Downloads folder only when you set a number of days.

Sources describe the default for cloud files differently. The support article says that on Windows 11 version 22H2 the default is to make OneDrive files online-only if they are not opened for 30 days⁸. The description of the management policy, on the other hand, says that if the policy is not configured, cloud files are not made online-only⁹. Check which value applies on your PC’s settings screen.

flowchart TB
        accTitle: How cloud files are made online-only again
        accDescr: Shows that Storage Sense makes cloud files that have not been opened for a while online-only again, that the files are not deleted, and that files set to Always keep on this device are excluded.
        A["Cloud files not opened for a while"] --> B{"Set to Always keep on this device?"}
        B -->|"Yes"| C["Excluded (stays on the PC)"]
        B -->|"No"| D["Storage Sense makes them online-only"]
        D --> E["The files are not deleted"]

Figure 6: Cloud files are not deleted; only the local copy is made online-only again.

Files that have been made online-only are downloaded again when you open them. From a business app’s point of view, this behavior can cause problems. The details are covered in “OneDrive Files On-Demand and Business Apps”.

What to Check Before Turning On Storage Sense

The usual trouble spots with Storage Sense are the Downloads folder and the Recycle Bin. In both, your own files can be deleted automatically.

Before turning it on, check these three things.

1. Does the number of days for deleting from the Downloads folder suit how you use it?
2. Are there files in the Recycle Bin that you may want to restore later?
3. On a company PC, has an administrator already decided the settings by policy?

On company PCs, administrators can turn Storage Sense on or off by policy. If a policy turns it on, users cannot turn it off⁹.

On Windows 11, Use “Cleanup Recommendations”

When you want to choose what to delete from a list yourself, use “Cleanup recommendations”. Microsoft explains that if you don’t want to use Storage Sense, you can use this to find and delete temporary files and system files⁷.

To open it, go to “Settings” → “System” → “Storage” → “Cleanup recommendations”. In Microsoft’s Japanese documentation the item has a different name from the one shown on the Japanese screen of the Windows 11 (26H2) machine we checked¹¹. It has the following four categories¹¹.

• Temporary files
• Large or unused files
• Files synced to the cloud
• Unused apps

Select the items to delete in each category and select that category’s “Clean up” button to delete them⁷. Your own files also appear in the list, so before pressing the button, check each checked item one by one.

flowchart TB
        accTitle: How to use Cleanup recommendations
        accDescr: Shows the flow of opening Cleanup recommendations from Storage in Settings, selecting the items to delete in each category, checking that none of your own files are included, and then selecting each category's Clean up button.
        A["Settings → System → Storage"] --> B["Open Cleanup recommendations"]
        B --> C["Select items to delete in each category"]
        C --> D["Check that your own files are not included"]
        D --> E["Select the category's Clean up button"]

Figure 7: In Cleanup recommendations, select items per category and check them before deleting.

When to Use Disk Cleanup Instead

Disk Cleanup (cleanmgr.exe) is a cleanup tool included with Windows. It can delete temporary files and system files and empty the Recycle Bin⁵.

In Microsoft’s support article, the Disk Cleanup steps are listed as the instructions for Windows 10. There it says that on systems without Storage Sense, you can use Disk Cleanup to delete temporary files and system files⁷. The Windows 11 instructions point to the “Cleanup recommendations” described above⁷.

There are two things to watch for when using Disk Cleanup⁷.

• When you first open it, three items are checked by default: Downloaded Program Files, Temporary Internet Files and Thumbnails
• To delete system files as well, select “Clean up system files” and choose the drive again

How you decide what to delete is the same as in the Settings app. Check each checked item one by one.

Note that Microsoft’s published list of “features no longer in development in Windows” (as of September 23, 2026) did not include Disk Cleanup¹². You may come across claims that it is being replaced by Storage Sense, but that cannot be confirmed from this list.

flowchart TB
        accTitle: Choosing a tool to free up space
        accDescr: Shows to use Storage Sense to clean up automatically, Cleanup recommendations to choose from a list on Windows 11, and Disk Cleanup to choose on Windows 10.
        A{"How do you want to clean up?"} -->|"Automatically"| B["Storage Sense"]
        A -->|"From a list (11)"| C["Cleanup recommendations"]
        A -->|"Windows 10"| D["Disk Cleanup"]
        B --> E["Check the day settings"]
        C --> F["Check the checked items"]
        D --> G["Can also select system files"]

Figure 8: Choose the tool by whether you want automatic cleanup or to pick from a list.

What Not to Delete by Hand

The items so far can be deleted from the Settings app or Disk Cleanup. Some things, however, must not be deleted by hand in File Explorer. This section covers three of them: WinSxS, the page file and restore points.

The WinSxS Folder

C:\Windows\WinSxS is a folder called the component store, and it contains Windows components and older versions of components replaced by updates. It can look large, but Microsoft warns that deleting files from WinSxS, or deleting the whole folder, can leave the PC unable to start or unable to install updates⁵.

Windows reduces this folder automatically. A Task Scheduler task called StartComponentCleanup cleans up old components while the PC is not in use. When it runs automatically, it deletes only old versions of components that were replaced at least 30 days earlier⁵.

To make it smaller right away, use the following command in an administrator command prompt⁵.

Dism.exe /online /Cleanup-Image /StartComponentCleanup

Unlike the task, this command deletes old versions without the 30-day grace period⁵. If you also add /ResetBase, none of the installed updates can be uninstalled anymore⁵. As long as you might need to roll back an update, don’t add /ResetBase. This command without /ResetBase was run in an administrator command prompt on Windows Server 2022 and confirmed to run to completion.

flowchart TB
        accTitle: How to make WinSxS smaller
        accDescr: Shows that WinSxS is not deleted by hand but made smaller with the automatic task or DISM StartComponentCleanup, and that adding ResetBase makes existing updates impossible to uninstall.
        A["WinSxS is large"] --> X["Delete by hand (not allowed)"]
        A --> B["Automatic task (30-day grace period)"]
        A --> C["DISM (no grace period)"]
        C --> D["Add /ResetBase"]
        D --> E["Existing updates can't be rolled back"]

Figure 9: Don’t delete WinSxS by hand; make it smaller with the methods Windows provides.

The Page File

The page file is a hidden system file on disk. It is used to move rarely used memory contents to disk and to raise the upper limit of usable memory (the commit limit). It may also be used to record what happened when Windows stops abnormally (a system crash dump)¹³.

flowchart TB
        accTitle: What the page file does
        accDescr: Shows that the page file moves rarely used memory contents to disk, raises the commit limit and supports system crash dumps, and that reaching the commit limit can make apps hang or crash.
        A["Page file"] --> B["Moves memory contents to disk"]
        A --> C["Raises the commit limit"]
        A --> D["Supports crash dumps"]
        C -.-> E["Apps may hang when the limit is reached"]

Figure 10: The page file supports the commit limit and crash dumps, so don’t delete it to free up space.

When the commit limit is reached, apps cannot allocate memory and may hang or crash¹³. Even if you are concerned about the space it takes, the page file is not something to delete to free up space. How to read the page file’s contents and size is explained in “What Does Windows’ “Memory Usage” Actually Mean?”.

Space Used by Restore Points

Restore points created by “System Protection” also use space. To reduce it, don’t look for files and delete them; set an upper limit on the space it may use in the “System Protection” settings screen. Microsoft’s support article explains that the slider on this screen sets the maximum space System Protection can use¹⁴.

A Guide for When You’re Unsure

Finally, here is a summary of what can be deleted.

flowchart TB
        accTitle: A guide to deciding what can be deleted
        accDescr: Shows that before deleting, you check in order whether your own files are included, whether you plan to go back to the previous Windows, and whether Windows uses it to run, and how to handle each case.
        A["What you're about to delete"] --> B{"Does it contain your own files?"}
        B -->|"Yes (Downloads, Recycle Bin, Users in Windows.old)"| C["Open it and move what you need first"]
        B -->|"No"| D{"Do you plan to go back to the previous Windows?"}
        D -->|"Yes"| E["Keep Windows.old"]
        D -->|"No"| F{"Does Windows use it to run?"}
        F -->|"Yes (WinSxS, page file)"| G["Don't delete by hand; use the dedicated method"]
        F -->|"No"| H["Can be deleted from the Settings app"]

Figure 11: Check, in order, for your own files, your plans to go back to the previous Windows, and whether Windows uses it to run.

• Windows.old: If you have no problems with the new Windows, you can delete it. Once deleted, you cannot go back to the previous Windows. If you wait, it disappears automatically after 10 days. Before deleting it, check the Users folder inside for any files you still need.
• Windows Update Cleanup and Delivery Optimization Files: Windows created these for its work, so you can delete them.
• Downloads and the Recycle Bin: These are your own files. Open them and move what you need to another location before deleting.
• Storage Sense: If you turn it on, check the day settings for Downloads and the Recycle Bin first.
• WinSxS and the page file: Don’t delete them by hand in File Explorer. Make WinSxS smaller with DISM or Windows Update Cleanup in Disk Cleanup.

Apart from running out of space, we often hear about PCs that are slow because disk usage is stuck at 100%. How to investigate that case is explained in “Disk at 100%: What Do You Actually Have to Stop?”.

Related Articles

• Disk at 100%: What Do You Actually Have to Stop? — Telling SysMain, Windows Search, and Defender Apart
• OneDrive Files On-Demand and Business Apps — The Assumptions Placeholders Break and How to Fix Them
• What Does Windows’ “Memory Usage” Actually Mean? — Reading Working Set, Private Bytes, Commit, and the Page File Correctly

References

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Frequently Asked Questions

Questions commonly asked at the time of consultation about the topic of this article.

Can I delete the Windows.old folder?

If you don't need to go back to the previous version of Windows, you can delete it. Windows.old contains the files needed to go back to the previous Windows, and once you delete it you cannot go back. Ten days after the upgrade, the previous version of Windows is deleted automatically. If you delete it yourself, the easiest way is from System > Storage in Settings. However, if you chose "Nothing" in "Choose what to keep" during the upgrade, your personal files were not moved to the new Windows and remain in Windows.old for only 10 days. Before deleting it, check the Users folder inside Windows.old for any files you still need.

Can I delete every item listed under "Temporary files"?

Avoid deleting everything at once; check each item. Windows Update Cleanup and Delivery Optimization Files are working files that Windows created. Downloads, on the other hand, is where you saved your own files, and once you empty the Recycle Bin the files in it cannot be restored. Deleting the previous Windows installation means you can no longer go back to the previous Windows.

If I turn on Storage Sense, will files in my Downloads folder be deleted too?

Deleting files in the Downloads folder is a separate setting. According to the description of the management policy, files in the Downloads folder are not deleted unless this is configured. If you specify a number of days, files that have not been opened for that many days or longer are deleted, so check the value on the settings screen before turning it on.

Can Disk Cleanup no longer be used?

Microsoft's support article points Windows 11 users to Cleanup recommendations in Settings. On the Japanese screen of Windows 11 (26H2), the item has a different name from Microsoft's documentation. The Disk Cleanup steps are listed as the instructions for Windows 10. Either way, the point is the same: check what you are deleting before you run it.

The WinSxS folder is large. Can I delete its contents?

Do not delete it by hand. Microsoft warns that deleting files or folders in WinSxS can leave the PC unable to start or unable to install updates. To make it smaller, use DISM /StartComponentCleanup or Windows Update Cleanup in Disk Cleanup.

Author Profile

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Go Komura

Representative of KomuraSoft LLC

Focused on Windows software development, technical consulting, and bug investigation, with particular strength in projects where existing assets remain and in investigating failures whose cause is hard to see.