How to free up RAM cache on Mac?

That is normal and it is a bad idea to try and micro manage Memory.

Cached Files: is memory that is held to help reopen frequently used app's.

It can be tapped into like free memory, when it is needed to open other app's.

see > View memory usage in Activity Monitor on Mac - Apple Support

If your Memory Pressure is running green or even yellow, then there is no need to worry or try and micro manage memory.

If your Memory Pressure is running in the Red, then you need to:

1) Restart more often.

2) Run less App's at the same time.

3) Replace that Mac with one that has more Memory.

Completely idle RAM is RAM that is not doing any work for you.

This is why, when macOS has free RAM, it tries to use a lot of it for Cached Files. The theory is that if the system wants the cached data before it wants RAM, the cache saves a slow trip to a SSD or mechanical hard disk. If the system wants the RAM, the cached data can be thrown away, because the cache is just a copy – the original data presumably is still available (albeit with higher retrieval cost) on the SSD or mechanical hard drive.

Cached Files are a performance optimization, and if you could force your Mac to dump those Cached Files to "free up this space", you could find your Mac running a bit more slowly.

If your Mac has a lot of RAM, and your workload does not need very much of it, macOS may decide to store more Cached Files to put the "idle" RAM to good use. Here, a Mac that has 32 GB of RAM has put nearly all of it to use either for actual Memory Used, or for Cached Files. (The numbers add up to slightly more than 32 GB – so there might be something going on like the values not being calculated as part of a single transaction.)

You should not be worried about Cached Files – but about keeping Memory Pressure green, and keeping the Swap Used to a reasonable number. Note here that macOS did a small amount of swapping to "Compressed RAM" – but none at all to the SSD, indicating that the memory system was completely unstressed.

Don't worry about it unless you are having problems.

All Macs are designed to use most of the memory all the time . . . even when idling.

This leads the uninitiated to believe that they have not got enough RAM and they spend a fortune getting another machine with as much RAM as possible only to find that most of that is being used whilst idling!

Just keep an eye on the Memory Pressure graph in Activity Monitor's Memory view. As long as it's in the green zone the system is fine. I have a Mini 2025 Mini M4 with 16 GB of RAM and it's never been in the yellow zone except one time when I was testing a 550 Mb image that I was trying to edit. That's way out of the normal workflow on a Mac.

Restart in Safe Mode, then restart normally.

Just ignore it! Unless you really understand what you are looking at you are more likely to worry yourself unnecessarily.

These things are there to troubleshoot when something goes wrong, so as long as your Mac is working well you can disregard the figures . . . . most users do not even know that Activity Monitor etc. exists.