Apple - How many files in a folder is too many?

You can easily try this yourself by running the following in Terminal

mkdir ~/t
cd ~/t
dd if=/dev/random of=test bs=1024 count=16
for i in {1..10000}; do cp test test.$i; done

to create a folder containing 10'000 files with 16kB each (replace the 16 in the third line with another number for differently sized files).

Answering considering a practical example: I have now 326.000 files in a folder, created by an application that download bits from a server. The files are zipped XML files, and my application extracts XML data from it and store it on a local database.

The application runs from the command line. Everything works fine without any issue but rm * or ls * does not work due to the expansion of the wildcard (error message Argument list too long). Since the files are stored in a temporary folder I can just remove the folder after processing the files.

I didn't try to open the folder with Finder, though. I suspect that could be very slow if possible at all.

Seems that around 10,000 is safe. However, I've found that if you go a lot higher like 50,000 Finder will never even list the files in the directory when you try to browse it. I suspect this is why a lot of data recovery software will create a new folder every 10,000 files if you're doing file carving in RAW.