It is safe to remove ‘Temp’ data, cashed data, browser’s data, cookies..
You can use the free portable ccPortable… or use the build-in disk cleanup…

To clean up after Windows use the built-in cleaner. Windows temp files return as soon as you fire up Windows so there is no point going mad trying to keep them at bay.
If you are running low on disk space, the usual suggestion is to get a bigger disk – upgrade to an SSD for major speed improvement.

To clean up the Windows way.
Open Windows Explorer.
Right click on drive C:
Select Properties.
Click on the Disk Cleanup button.
Select the items you want.

cheers, Paul

In addition to PaulT’s post, I recommend using the ‘clean up system files’ button to release old patch installation files and various other temp files. These can amount to gigabytes in unecessary space if left unattended. There’s a good diagramatic tutorial available over on Ten Forums to help you with this.

Deleting temporary files may not free up as much space as think it would. Beginning with Windows 10 1903 a certain amount of storage is reserved by Windows. See Windows 10 and reserved storage for a more detailed explanation.

Concerning PreFetch: Deleting the folder or its contents is pointless, as it is dynamically rebuilt. Do a Search on [ prefetch folder ]; one hit is
https://windowsground.com/what-is-windows-prefetch-in-windows-10/ .

If Windows 10 is on an SSD, Prefetch is effectively adding needless I/Os to your SSD.  On a hard drive, having a ‘small’ mini-directory with copies of frequently used Windows internals will improve performance.  SSD I/O speed largely negates the need for a pre-fetch folder of files.  Maybe there’s a smidge of performance improvement with Prefetch, but I have my doubts.  Considering the extra CPU cycles needed to first search the mini-directory to find a module that may be there and maintaining that mini-directory vs searching the full Windows/System32 directory at SSD speed, I decided to turn it off completely.

I had to track it down, but disabling:  ‘Sysmain         Maintains and improves system performance over time’ in services (Win 10 v1909) put an end to it.  Did I notice any slowdown since disabling it?  None whatsoever.

But then, I’m running an overclocked 8 processor system that I keep tweaking endlessly to stop running useless Windows 10 garbage from bloatware to things like Bluetooth that do not exist in my computer.  As of last count, I had 70 services disabled.  Makes for a lightning fast boot up as well rocket speed everything else.

In addition to Windows/Temp, I regularly clean out Users/<userid>/appdata/local/temp, Users/<userid>/appdata/Roaming/Microsoft/Windows/Recent Items, and the cache files from Firefox: Users/<userid>/appdata/Local/Mozilla/Firefox/Profiles/xxxxxxxxx-default-release/cache2/entries, to name a few.  To me, fewer items in the SSD directory speeds things up, a couple nanoseconds at a time.  And yes, I wrote my first assembler code in 1967.  I’m still a computer efficiency freak.

bratkinson wrote:

If Windows 10 is on an SSD, Prefetch is effectively adding needless I/Os to your SSD

I think you’ll find Windows automatically disables this on SSDs. Manually disabling it means it’s unavailable for any spinners you have installed.

cheers, Paul

What is the safest way to remove same, if at all?

Set Storage Sense to remove temporary files automatically every day, week or month:

How to use Windows 10’s Storage Sense to free up Disk Space