You're dragging a folder from your Mac to a USB stick or external hard drive. It's a FAT32 or exFAT partition. Halfway through the copy, Finder stops and throws up that cryptic alert: "The operation couldn't be completed. (OSStatus error -36.)". Sometimes it happens with a single file, sometimes after copying hundreds. Either way, it's annoying and stops you cold.
I've seen this on every macOS version from Mojave to Sonoma. It's not your drive dying and it's not a permissions problem. The culprit is almost always a filename or metadata issue that the older filesystem can't handle. FAT32 and exFAT don't support certain characters or extended attributes that macOS uses by default.
What's actually happening
When you copy a file to a FAT/exFAT drive, macOS tries to write extra metadata — things like Finder tags, icon positions, or extended attributes. The destination filesystem either chokes on that data or on a character in the filename that it considers invalid. The result? Error -36. It's not corruption. It's a translation failure between modern macOS and older filesystem standards.
One real-world trigger: you exported a file from Pages or Word with a name like Quarterly Report: Final. That colon is a big problem. On FAT32/exFAT, colons aren't allowed (on macOS they're allowed but converted to slashes on Windows). So when Finder tries to write it, the whole operation dies.
How to fix it
Here's a step-by-step that gets you out of this in under five minutes. Start with the first one — it solves 80% of cases.
- Rename the file(s) to something plain. Remove colons, slashes, question marks, asterisks, and other special characters. Use underscores or spaces instead. For example, change
Report: Final.v2toReport_Final_v2. Try the copy again. - Strip extended attributes. If renaming doesn't work, there might be weird metadata attached. Open Terminal in the folder where the file lives and run:
xattr -c filenameReplace filename with the actual file name. Use sudo xattr -rc foldername for a folder and everything inside it. Then try the copy.
- Zip the files first. This bypasses the problem entirely. Create a ZIP archive of the folder on your desktop, then copy the ZIP to the external drive. The archive doesn't carry the same metadata baggage and the filename is under your control. Downside: you have to unzip on the other end. But it works when nothing else does.
- Reformat the drive to APFS or Mac OS Extended. If you only use the drive with Macs, that's the real fix. FAT32 and exFAT are for cross-platform compatibility. If you don't need Windows access, you don't need those filesystems. Back up the drive, open Disk Utility, erase it, and choose APFS or Mac OS Extended (Journaled). That eliminates the class of errors entirely.
What to check if it still fails
If you've renamed files, stripped attributes, and the error persists, look at the drive itself. Is it a USB hub or front-port connection? Drives sometimes drop off mid-copy, and the error is just a symptom of a flaky connection. Plug it directly into your Mac's port and try again.
Also, check the drive's format. Right-click the drive on your desktop and click Get Info. It'll say MS-DOS (FAT32) or ExFAT. If it says something like "NTFS" — that's a whole different problem. macOS can read NTFS but not write to it out of the box. Error -36 is actually what you'd see. For that, you'd need a third-party NTFS driver or reformat to a Mac-friendly format.
One more thing: if you're on an older Mac with a spinning hard drive, the drive itself might be failing. Check with fsck_exfat or fsck_msdos in Terminal, but honestly — the software fixes above cover 95% of cases. I've done this dozens of times and only once was it actual drive failure.
Bottom line: error -36 is a formatting mismatch, not a calamity. Rename first, strip metadata second, zip as a fallback, and reformat if you don't need cross-platform. You'll be back to copying in no time.