## TL;DR
Windows needs working room on the system drive, roughly 8 to 10 GB free for cumulative updates and more for feature updates, because it stages the new payload beside the old one. Free space deliberately: run Disk Cleanup with system files (which clears old update copies), move or extend where possible, clear the SoftwareDistribution download cache, and check the WinSxS size honestly with DISM instead of deleting from it manually.

```text
windows update failed not enough disk space to install
```

## Use this when
- Updates fail and Settings or the Update Assistant cites low storage.
- The system drive shows under 5 GB free on a small SSD or VM.
- Feature updates fail while monthly cumulative updates still squeeze through.

## Not for this skill when
- The full disk is a data volume, not the system drive. Update staging does not use it.
- Space is plentiful but updates still fail. The code is pointing elsewhere; read it.

## Steps
1. Measure free space and the big consumers: DISM /Online /Cleanup-Image /AnalyzeComponentStore for WinSxS real size, and a disk usage scan of user profiles. Verify: you know the top space consumers by size
2. Run Disk Cleanup (cleanmgr) with Clean up system files and select Windows Update Cleanup and temporary files. Verify: the tool reports gigabytes reclaimed
3. Run DISM /Online /Cleanup-Image /StartComponentCleanup to consolidate superseded components. Verify: AnalyzeComponentStore afterwards shows a smaller store and cleanup recommended as No
4. Clear the Windows Update download cache by stopping the update service and removing the SoftwareDistribution Download contents. Verify: the pending failed payload is gone and will re-download
5. Retry the update; for feature updates on very small drives, attach external storage when setup offers that option. Verify: the update installs to completion

## Variant phrasings
### windows update not enough space cleanmgr update cleanup
The cleanup-action phrasing.
### feature update needs more space small ssd fix
The small-drive phrasing.
### DISM StartComponentCleanup winsxs too big
The component-store phrasing.

Compatibility: Compatibility: Windows 10 and 11; reserved storage on modern builds changes how much must be free.

## Why it happens
Update servicing is copy-forward: the new component versions are staged and committed while the old ones remain for rollback, so peak usage is much larger than the download size. Machines upgraded for years accumulate superseded components in WinSxS that only the servicing tools can safely consolidate; manual deletion inside WinSxS corrupts the store.

## Edge cases / pitfalls
- Never delete files inside WinSxS or the Installer folder by hand; both are servicing-owned and hardlinked.
- VM fleets: expanding a thin disk is often faster than forensic cleanup, but do it before the patch window, not during.
- The hibernation file and page file are large on small drives; disabling hibernation is a legitimate space lever on desktops, less so on laptops users rely on for fast startup.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_1YFhkYjtgrJVUdzgkXj98Q