Downloaded. Ran it. Tells me "900" files can be cleaned. No summary, no list. But I was at least asked to buy the app. Why would I buy the app if I have no idea if it'll help?
That said, keeping track of blocks and extents for deduplication would be a much more expensive problem to solve.
Back in the MS-DOS days, when the RAM was sparse, there was a class of so-called "memory optimization" programs. They all inevitably found at least few KB to be reclaimed through their magic even if the same optimizer was run back to back with itself and allowed to "optimize" things. That is, on each run they always find extra memory to be freed. They ultimately did nothing but claim they did the work. Must've sold pretty well nonetheless.
You may find this interesting: Investigations into SoftRAM 95 by Raymond Chen [1] and Mark Russinovich [2] respectively.
"They implemented only one compression algorithm.
It was memcpy."
[1] https://devblogs.microsoft.com/oldnewthing/20211111-00/?p=10...
[2] https://www.drdobbs.com/parallel/inside-softram-95/184409937
QEMM worked by remapping stuff into extended memory - in a time that most software wasn't interested in using it. It worked as advertised.
Quarterdeck made good stuff all around. Desq and DesqView/X were amazing multitaskers. Way snappier than Windows and ran on little to nothing.
> If some eligible files were found, the amount of disk space that can be reclaimed is shown next to the “Potential Savings” label. To proceed any further, you will have to make a purchase. Once the app’s full functionality is unlocked, a “Review Files” button will become available after a successful scan. This will open the Review Window.
I half remember this being discussed on ATP; the logic being that if you have the list of files, you will just go and de-dupe them yourself.
If you can do that, you can check for duplicates yourself anyway. It's not like there aren't already dozens of great apps that dedupe.
Most of those delete rather than use the features of APFS.
(Obviously it won't show the list until payment. That part is expected behavior.)