An unmodified install of any version of Windows newer than XP should be pretty good at memory management on its own, unless some processes aren't being shut down properly. I've had my PC running for weeks on end (Ryzen 7 5800X/16 GB) using a mix of web browsing, office, gaming (including modern intensive games like Robocop: Rogue City), and video editing software, and haven't noticed any issues with memory not being freed as needed. The general consensus over at Ars Technica for memory management in Windows post-XP is the following:

1. Install Windows.
2. Don't mess with memory management.
3. Use and enjoy your computer.

I wouldn't bother with this "memory freeing" software, as it's probably not doing much if anything to help at all. Windows is actually pretty good at putting unused data in system memory from active but idle processes into the swapfile, and freeing up memory when programs aren't using it (even if they terminate abnormally). About the only one of these "tweaking" programs that I still used beyond XP was Power Defrag, mainly because it would make Defrag run before the system booted fully and it would take much less time to execute back when I still used a mechanical hard drive as a boot drive.

Several of the big security vulnerabilities like heartbleed etc, were implemented by screwing around with memory, so it's possible that windows has updated itself to a version that doesn't let anything but windows mess around with the memory.

They are snake oil. By design, an app can't manage memory for the OS - that would mean any app could access memory globally and steal anything it wanted from other apps.

One misconception is windows is now a memory hog.
Modern versions of windows are designed to use whatever resources are available, if you have 16GB what would you prefer? it to use the memory you paid for or limit itself to 8GB and have that other 8GB remain untouched?
If something demands more memory the OS will downsize accordingly.

Not saying it's perfect. Its still very much a good idea to reboot your PC, but does it really need to be up 24/7 or can you give it a quick reboot say end of the day

There were few programs for Windows 3.1 and 9x that were not totally snake oil. But still most of them were. But for NT based systems, they are all snake oil.

I think i've only used two of those kind for Win95-98 in the day - some program that's just two sliders on a window ~1998, and Memokit ~2000 (which is really graphically dressed up and skinned and *looked* like it worked, but it was trialware). I stopped using these altogether when RAM became affordable and that was before the spyware/malware deluge with generic named programs marketing it up gaslighting you of being infected while they do their own payload.

I love texts that start with "As we all know..." followed by some fallacy. 😆

Other than that, I don't have much to add to what others (MadMac, chinny) already brought up. 😀

I don't know if they really work - memory cleaners and registry cleaners alike - , but at the end of the cleaning process, it does feel good to see all the green check marks saying the system is "cleaned". Never bought any for the Win 9x systems though. Bought 1 year license for CCleaner once during Win7 days.