How to fix 0x800f0821 error when installing optional features in Windows?

Error 0x800f0821 means the servicing job that adds an optional feature took too long, and Windows stopped it. Microsoft lists it as CBS_E_ABORT, a CBS transaction timeout. Restart the PC, close heavy programs and add the feature again before you try anything else (Fix 1).

Facts checked on 16 October 2026. Steps written for Windows 11 (25H2 and 26H2) and Windows 10 22H2.

What error 0x800f0821 means when you install an optional feature

0x800f0821 comes from Component Based Servicing (CBS), the part of Windows that adds and removes features, language packs and updates. Microsoft's list of common Windows Update errors names it CBS_E_ABORT and describes it as CBS transaction timeout exceeded. In plain words: the job started, ran longer than Windows allows, and the servicing stack stopped it.

That is why the error often feels random. The feature, the download and your Windows can all be fine. The job simply did not finish in time, usually because the PC was busy, slow or waiting for a restart. The same code can appear in three places:

Why the optional feature install times out with 0x800f0821

Old guides list corrupted files, network problems and update failures as equal causes. For this code the order is clearer, because Microsoft ties it to a timeout. These are the causes, from the most common to the rarest, each with the fix that answers it.

How to fix error 0x800f0821 in Windows 11 and Windows 10

Fixes 1 to 3 answer the timeout itself and solve most cases. Fixes 4 and 5 add the feature another way. Fixes 6 to 8 repair Windows Update and the component store, and Fix 9 is for .NET Framework 3.5 only.

Fix 1. Restart Windows and add the feature again on an idle PC

10 minutesNo riskEvery reader first, and especially when Windows Update shows a pending restart.

Microsoft says 0x800f0821 means the servicing job ran past its time limit. A pending restart or background updates hold the same servicing stack, so the feature waits in line and times out. A clean restart and an idle PC give the job the time it needs.

1. Save your work and select Start > Power > Restart. If Windows offers Update and restart, choose it and let it finish.
2. After the restart, wait five minutes so startup programs and background tasks settle.
3. Close games, video editors, virtual machines and large downloads.
4. On a laptop, plug in the charger so Windows does not slow down to save power.
5. On Windows 11 open Settings > System > Optional features and select View features. On Windows 10 open Settings > Apps > Apps & features > Optional features and select Add a feature.
6. Select the feature, select Next and Add (or Install on Windows 10), and wait without starting other heavy work.
7. Restart again if Windows asks for it.

Fix 2. Install all pending Windows updates, including the servicing stack

15 to 30 minutesLow riskWindows Update offers updates you have not installed yet, or you have not checked for a while.

Microsoft's mitigation for this code asks you to install KB4493473 or later. On a current PC that means the latest cumulative update, which carries the newest servicing stack. Pending updates also keep the component store busy, which makes a timeout more likely.

1. On Windows 11 open Settings > Windows Update. On Windows 10 open Settings > Update & Security > Windows Update.
2. Select Check for updates and install everything offered.
3. Restart when Windows asks, then check again until it says You're up to date.
4. Add the optional feature again the same way as in Fix 1.

If an update itself fails, run the troubleshooter first: Run the Windows Update troubleshooter. If one update keeps failing, download it from Microsoft and install it by hand: Install an update from the Microsoft Update Catalog.

Fix 3. Give the PC or virtual machine more memory, processor time and disk space

10 to 20 minutesLow riskA virtual machine, an older PC, a PC with little memory, or a system drive that is almost full.

Microsoft's own advice for 0x800f0821 is to increase the resources on the device and, in a virtual machine, add virtual CPU and memory to speed up the operation. A faster job finishes before the watchdog timer expires.

1. Press Ctrl + Shift + Esc to open Task Manager and look at CPU, Memory and Disk while you add the feature.
2. Close programs that use a lot of memory or disk, and pause cloud sync such as OneDrive until the feature is installed.
3. Open Settings > System > Storage and check that drive C: has free space. Free some if it is almost full: Free up disk space and delete temporary files.
4. In a virtual machine, shut it down, add virtual processors and memory in the VM settings, and start it again.
5. Add the feature again and leave the PC alone until it finishes.

Fix 4. Turn the feature on in Windows Features instead of Settings

5 minutesLow riskThe feature you need is in the classic Windows Features list, such as .NET Framework 3.5, Hyper-V or Windows Sandbox.

Settings > Optional features and Turn Windows features on or off are two different lists. When Settings fails, the classic window sometimes works for the features it holds, because it starts the change through another path.

1. Press Win + R, type optionalfeatures and press Enter. You can also search for Turn Windows features on or off.
2. Find the feature and select its box so it is filled.
3. Select OK, and choose Let Windows Update download the files for you if Windows asks.
4. Wait for Windows completed the requested changes, then select Restart now.

If this window stays empty or will not open, see our guide on Turn Windows features on or off not working.

Fix 5. Add the optional feature by name with DISM /Add-Capability

10 to 20 minutesLow riskSettings fails every time, or you need a capability such as Wireless Display, a language part or RSAT by its exact name.

Optional features in Settings are capabilities, and DISM installs the same capability directly. DISM shows its progress and the exact error, and it can take the files from a source you choose instead of Windows Update.

1. Right-click Start and select Terminal (Admin). On Windows 10 select Windows PowerShell (Admin). Select Yes in the User Account Control window.
2. Run DISM /Online /Get-Capabilities /Format:Table to list every capability and its state.
3. Find the line of your feature and copy its full Capability Identity, including the tildes and version.
4. Run DISM /Online /Add-Capability /CapabilityName: followed by that identity, as in the example below.
5. Wait until DISM reaches 100 % and shows The operation completed successfully, then restart.

DISM /Online /Get-Capabilities /Format:Table | findstr /i "wireless"
DISM /Online /Add-Capability /CapabilityName:App.WirelessDisplay.Connect~~~~0.0.1.0

Microsoft's DISM reference explains where DISM looks for files: first in a /Source you give, then in a location set by Group Policy, then on Windows Update unless you add /LimitAccess. On a home PC you normally add no source and let Windows Update provide the files.

Fix 6. Reset Windows Update components and run the Windows Update troubleshooter

15 minutesLow riskWindows updates fail as well, or downloads for features hang at the start.

Optional features download through Windows Update. A damaged update cache or a stuck update service can slow the job until it hits the time limit, and resetting the components gives the servicing job a clean start.

The reset stops the update services, renames the SoftwareDistribution and catroot2 folders and starts the services again. Step by step: Reset Windows Update components.

1. Open Command Prompt as administrator. Type cmd in the search box, right-click Command Prompt and select Run as administrator. Select Yes when Windows asks for permission.
2. Stop the update services. Type the commands below and press Enter after each one. If Windows says that other services depend on Cryptographic Services, it stops them too. A message that a service is not started is fine.

   net stop wuauserv
   net stop bits
   net stop cryptsvc

3. Delete the download queue files. This clears the list of downloads that the Background Intelligent Transfer Service keeps. If Windows says it cannot find the files, continue.

   del "%ALLUSERSPROFILE%\Application Data\Microsoft\Network\Downloader\qmgr*.dat"

4. Rename the update cache folders. Renaming keeps a copy in case you need it; Windows creates new, empty folders when the services start again. If you get Access is denied, a service is still running: repeat the previous step.

   ren %systemroot%\SoftwareDistribution SoftwareDistribution.old
   ren %systemroot%\System32\catroot2 catroot2.old

5. Start the services again. Type the commands below and press Enter after each one. The requested service has already been started is fine: Windows started it on its own.

   net start cryptsvc
   net start bits
   net start wuauserv

6. Restart and check for updates. Restart the PC. Then select Start > Settings > Windows Update > Check for updates. The first check can take longer than usual because everything is downloaded again.

These steps were written for Windows 11 and Windows 10 (the steps are the same). The full page with the other versions and what each result means: Reset Windows Update components

1. On Windows 10, also open Settings > Network & Internet > Status and select Network troubleshooter if downloads fail.
2. On Windows 11, check the connection with Settings > Network & internet, or follow How to check your internet connection in Windows.

Fix 7. Repair the component store with DISM RestoreHealth and SFC

20 to 30 minutesLow riskDISM or SFC reports damage, or several features and updates fail with servicing codes.

Features are added from the component store. If its records are damaged, CBS spends a long time checking and repairing before it can add anything, which can push the job past the time limit.

1. Open an elevated command window. Right-click Start and select Terminal (Admin), or type cmd in the search box, right-click Command Prompt and select Run as administrator. Select Yes when Windows asks for permission.
2. Run DISM first. Type the command below and press Enter. DISM downloads clean copies of damaged components from Windows Update, so it can take several minutes. Wait until it says The operation completed successfully.

   DISM.exe /Online /Cleanup-Image /RestoreHealth

3. Run System File Checker. In the same window, type the command below and press Enter. Do not close the window until the verification reaches 100%.

   sfc /scannow

4. Read the result and restart. Compare the last message with the table below this guide, then restart the PC so that repaired files are loaded.

These steps were written for Windows 11 24H2 and 25H2. The full page with the other versions and what each result means: Run DISM and SFC to repair Windows system files

Step by step, with what each result means: Run DISM and SFC to repair Windows system files. If RestoreHealth cannot reach Windows Update, Microsoft's DISM options let you point it at mounted Windows media of the same version with /Source and /LimitAccess.

Fix 8. Check that the Windows Modules Installer service is not disabled

5 minutesLow riskA cleanup tool or a tweak guide changed services, or the service shows Disabled.

Windows Modules Installer (TrustedInstaller) is the service that installs and removes Windows components. If it is disabled, servicing jobs cannot run properly. Its normal startup type is Manual: Windows starts it when needed.

1. Press Win + R, type services.msc and press Enter.
2. Scroll to Windows Modules Installer and double-click it to open Properties.
3. If Startup type is Disabled, set it to Manual and select Apply.
4. Select Start if the service is stopped, then OK.
5. Restart and add the feature again.

Do the same check for Windows Update and Background Intelligent Transfer Service. More on services: Check and restart Windows services.

Fix 9. Install .NET Framework 3.5 from Windows installation media

20 to 30 minutesLow riskThe feature you need is .NET Framework 3.5 on Windows 10 or Windows 11 25H2 and earlier, and the other fixes did not help.

Windows media holds the .NET 3.5 files in its sources\sxs folder. With /LimitAccess DISM takes the files from there and skips Windows Update, so the download part of the job is gone.

1. Check your version with Win + R, winver, OK.
2. Download the ISO of the same Windows version and language from Microsoft's own download page.
3. Right-click the ISO file and select Mount. Note its drive letter, for example D:.
4. Open Terminal (Admin) and run the command below with your drive letter.
5. Restart when DISM shows The operation completed successfully.

DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /Source:D:\sources\sxs /LimitAccess

If error 0x800f0821 is still there

The CBS log shows which part of the job ran out of time. Look at the lines just before the timeout, at the same time as your last attempt.

1. Press Win + R, type notepad C:\Windows\Logs\CBS\CBS.log and select OK. If Notepad says the file is in use, copy it to the desktop first and open the copy.
2. Press Ctrl + End to jump to the newest lines.
3. Press Ctrl + F and search upward for 0x800f0821 or CBS_E_ABORT.
4. Read the package or capability name a few lines above it: that is the part that took too long.
5. If you used DISM, also open C:\Windows\Logs\DISM\dism.log and check the last lines.

For Microsoft support or your IT department, send the feature name, your edition and build from winver, the time of the failure and the CBS.log lines around it. 0x800f0821 is not a licence or account limit. Repeated timeouts on a PC that is idle and fully updated can point to a failing or very slow disk: check the drive's health in Settings > System > Storage > Advanced storage settings > Disks & volumes.

How to keep error 0x800f0821 from coming back

Frequently asked questions

What does error 0x800f0821 mean?

It means the servicing job that installs a feature or update ran out of time. Microsoft lists 0x800f0821 as CBS_E_ABORT, client abort, IDABORT returned by ICbsUIHandler method except Error(), and describes it as CBS transaction timeout exceeded. The servicing stack watchdog timer expired before the job finished, so Windows stopped it. Nothing is usually broken. Restart, let the PC go idle and add the feature again (Fix 1).

How do I fix 0x800f0821 when adding an optional feature in Windows 11?

Restart first and add the feature again with no heavy programs running, from Settings > System > Optional features > View features (Fix 1). Install all pending Windows updates (Fix 2), because Microsoft names updates as part of the mitigation. If the PC is slow or a virtual machine, give it more memory and processor time (Fix 3). If Settings keeps failing, add the capability by name with DISM /Add-Capability (Fix 5).

Does 0x800f0821 happen on Windows 10 too?

Yes. The code comes from Component Based Servicing, which works the same way on Windows 10 and Windows 11. On Windows 10 the optional features page is Settings > Apps > Apps & features > Optional features > Add a feature. The fixes are the same. Windows 10 reached the end of support on 14 October 2025, so a Windows 10 22H2 PC without Extended Security Updates no longer gets security fixes.

How do I install Wireless Display with DISM?

Open Terminal (Admin) and run DISM /Online /Add-Capability /CapabilityName:App.WirelessDisplay.Connect~~~~0.0.1.0, then restart when DISM reports The operation completed successfully. Before that, check the exact name on your PC with DISM /Online /Get-Capabilities /Format:Table, because the identity must match letter for letter. If DISM shows Error: 0x800f0821, restart, install pending updates and try again with nothing else running (Fixes 1 and 2).

Why does the optional feature install stay at the same percent for a long time?

Because CBS is still working on the package, checking the component store and writing files, and the progress bar only moves at certain stages. Large features and language packs take longer on slow disks and in virtual machines. Cancelling and starting again repeats the whole job. Let it run with the PC idle. If it then fails with 0x800f0821, the job ran past its time limit: free resources with Fix 3 and try again.

Is 0x800f0821 caused by a virus or by my antivirus?

Microsoft does not name either as a cause: it ties the code to a servicing timeout. A full or busy security scan can slow the PC while a feature installs, so let a running scan finish first. Do not turn protection off for good. If you suspect malware, run a full scan with Microsoft Defender and add the feature after it ends, when the PC is idle.

What is KB4493473 and do I need it?

It is the update Microsoft names in its mitigation for 0x800f0821: make sure that the device has installed the update in KB4493473 or later. On a current Windows 10 22H2 or Windows 11 PC you do not search for that one update. You install all cumulative updates offered in Windows Update, because they carry the newer servicing code. Fix 2 shows how, and Fix 2 also links the manual install route.

Can I install optional features without the internet?

Partly. Microsoft's DISM reference says DISM looks for files first in a /Source you give, then in a Group Policy location. Only then does it use Windows Update, and /LimitAccess turns that last step off. .NET Framework 3.5 can be added from the sources\sxs folder of Windows media of the same version (Fix 9). For other capabilities we could not confirm that a consumer Windows ISO contains their files, so a home PC normally needs Windows Update.

Is 0x800f0821 the same as 0x800f081f or 0x800f0954?

No. Microsoft lists 0x800f081f as CBS_E_SOURCE_MISSING, which means the source files for a package were not found, often with component store damage. 0x800f0821 is a timeout: the job had what it needed but took too long. We did not check the meaning of 0x800f0954 today, so we do not describe it here. For 0x800f081f, the source and RestoreHealth steps in Fixes 5 and 7 are the better place to start.