Can folders become too full of items?

Question

I have recently had 2 folders become too full of items. I can save items (bookmarks and backups) to the folder but they do not register and there is no error message saying nothing happened. Result is I do not have some bookmarks I wanted to keep and worse the most recent backups are not there (as a program auto updated and crashed, waiting on feedback from provider) to be able to restore data.

Is this normal or do I have malware or something affecting my computer?

MacBook Pro on Big Sur

Further info: storage 251gb 72gb free, files overflowing the folder are zip files from my accounts package upto 18mb each. Bookmarks are in Safari so not sure how/where they are stored. I tend to be a click only user, hence bad house keeping but it would be nice to get a warning files were being tossed over the side and not kept.

Answer 1

It would be difficult to reach the maximum number of files or folders on an APFS volume; the older HFS+ format, however, has significantly smaller limits as well as data structures that can become corrupted over time.

Try restarting into Recovery Mode and running Disk Repair on the volume or disk that contains your problematic folder(s).

Answer 2

From what I've read, a given MacOS folder can hold up to 2.1 billion items. That may be lower if you're using a particularly old system, but it still takes an extraordinarily large number of items.

However, you will run into performance issues well before that limit. Whenever a folder is opened, the Finder has to do a lot of work sorting files, displaying icons, generating sizes, etc, and this increases exponentially as the number of files increase. You may also have some mild corruption in the file system which would slow things down further. I'd run disk utility on the volume just to be safe, and try to structure your files into smaller groups.

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P.s… I should add that if you access the folder from the command line (using the Terminal app) you should be able to avoid most performance issues. If you're having trouble opening the folder in the Finder, use the command line to organize the files (moving them into subfolders and such). The Finder processes files when a folder is opened, so you can have as deep a hierarchy as you like without affecting performance, as long as the number of items at any given level is reasonable.