Free up disk space on Windows without a registry cleaner

A full system drive is usually four or five large things rather than thousands of small ones. If you clear those in the right order you will normally get tens of gigabytes back in about twenty minutes, without installing anything and without touching the registry.

Why registry cleaners are not the answer

It is worth saying this early, because it is the first suggestion many people meet. Registry entries are tiny. Even a very messy registry takes up a few megabytes, so cleaning it cannot free meaningful space on a drive measured in hundreds of gigabytes.

The registry is also a live database that Windows and your installed programs depend on. Removing entries that a cleaner has guessed are unused occasionally breaks something in a way that is hard to trace weeks later. The risk is small, but so is the reward, and there is no reason to accept even a small risk for a few megabytes.

Look before you delete

Before removing anything, find out where the space has gone. Guessing leads to people deleting things they needed and still being short of room.

Windows has this built in. Open Settings, go to System, then Storage. You get a breakdown by category: apps, temporary files, documents, and so on. Click into any category to see the largest items. That view is enough to tell you whether your problem is a Steam library, a folder of video, years of downloads, or Windows itself.

If you would rather see it as a folder tree sorted by size, any disk usage viewer will show you the same thing arranged differently. The point is simply to look first.

The big wins, in order

These are ordered by how much space they typically return against how little they risk. Work down the list and stop when you have enough.

1. Windows Update leftovers. Usually the single biggest recovery, and often several gigabytes. Search for Disk Cleanup, run it, choose your system drive, then click the button marked Clean up system files. Wait for it to scan again, then tick Windows Update Cleanup along with the temporary file categories. This removes superseded copies of update files that Windows keeps in case you roll back.
2. The previous Windows installation. After a feature update, Windows keeps your old installation in a folder called Windows.old so you can go back. It is often 15 to 20 GB. Windows deletes it automatically after ten days, but if you are short now, Disk Cleanup offers it as Previous Windows installations. Only remove it if the current version is behaving itself, because this is the thing that lets you undo the update.
3. The hibernation file. Windows reserves a hidden file on your system drive to store memory contents when the machine hibernates. It is sized as a proportion of your installed memory, so on a machine with plenty of RAM it can be several gigabytes. If you never hibernate, you can reclaim it. Open Command Prompt or Terminal as an administrator and run powercfg /hibernate off. Be aware this also turns off Fast Startup, so a cold boot may take a little longer. To put it back, run powercfg /hibernate on.
4. System Restore. Restore points are useful, but the space set aside for them can grow. Search for Create a restore point, select your drive, click Configure, and look at the current usage against the maximum. Reducing the maximum to around 5 per cent of the drive keeps the safety net while returning the rest. Do not disable it altogether, because it is genuinely worth having.
5. Downloads, and what is in it. This folder quietly collects installers you already ran and files you already used. It is frequently the largest single folder of genuinely disposable content on a machine, and nothing in Windows clears it for you unless you ask.
6. Cloud folders storing local copies. If you use OneDrive, Dropbox or similar, check whether files are being kept on the disk as well as in the cloud. OneDrive calls the setting Files On Demand. Turning it on keeps everything available while only downloading what you open, which on a large account can free a great deal.

The component store, and how to handle it

If you have looked at folder sizes you may have found C:\Windows\WinSxS reported as enormous, sometimes 10 GB or more. This is the component store, and it holds the pieces Windows uses to repair itself and to uninstall updates.

Two things are worth knowing. First, the size reported by File Explorer is misleading, because many of the files in there are links to files that exist elsewhere and are counted twice. The real figure is smaller than it looks. Second, you must never delete anything inside it by hand. That is one of the few genuinely destructive things you can do to a Windows installation.

There is a supported way to trim it. In an administrator Command Prompt, run:

Dism.exe /Online /Cleanup-Image /StartComponentCleanup

This removes superseded components safely and takes a few minutes. There is a stronger version that adds /ResetBase, which frees more, but it also means you can no longer uninstall any update installed up to that point. On a machine that is running well, that is usually an acceptable trade. On a machine you have just updated and are not yet sure about, leave it out.

Keeping the space you got back

Storage Sense will do most of this maintenance for you. It is in Settings, System, Storage. Turn it on and open its settings, and you can have Windows clear temporary files automatically, empty the recycle bin after a set number of days, and remove downloaded files you have not opened in a while.

That last option deserves a moment's thought before you enable it, since it deletes from your Downloads folder on a timer. If you treat Downloads as a temporary area it is ideal. If you use it as storage, leave it off and tidy it yourself.

Things to leave alone

If you are still short of space after all of this, the problem is almost certainly your own files rather than Windows. Games, video projects and photo libraries are the usual culprits, and the fix there is either a second drive or moving the largest library somewhere else. No amount of system cleaning will substitute for it.