auslogics[.]com/en/software/registry-defrag/
This is a small free app with a minimal impact on Windows from installing it. Currently you'll also get an offer for a free copy of their BItReplica app, which is file backup / sync software.
Ignore the hype on the Auslogics web page. If you open Notepad, type something, then hold down the enter key to insert Loads of blank lines, & then type something else, the resulting file when you save it is going to be larger than if you skipped adding all those empty lines. That's basically what Auslogics Registry Defrag does, remove all the empty lines. The result is not likely to be Earth shattering -- I used it [& have used similar] simply as a matter of good housekeeping, though there are probably some Windows installs that will see something noticeable.