The classic negative-number Mac errors, what they mean in plain language and what usually fixes them.
macOS still speaks a dialect designed in 1984: negative numbers (OSStatus codes) from the original Macintosh Toolbox, and they surface everywhere once you start looking, Finder copy errors, keychain failures, AppleScript complaints, LaunchServices refusals. The famous ones earn their fame honestly: -36 is a genuine disk I/O problem that deserves a drive-health check, -43 is simply 'not there', -50 is a program passing nonsense to the system, and -10810 means the app-launching machinery itself has stumbled. This directory covers the codes Mac users actually encounter, with the historical name (which is what searching documentation requires) and the modern first move.
A note on -36 in particular, because it drives more panic than the rest combined: it means a read or write failed at the storage layer. On a healthy modern SSD it often traces to one corrupt file or a dying external drive rather than the internal disk, copy files individually to isolate the bad one, and check the volume in Disk Utility before assuming the worst. Any recurring I/O error, though, is a backup-now signal: storage that complains twice rarely stops at twice.
Why are Mac error codes negative? The original Mac system software returned negative numbers for errors (0 and positive meant success or data). Forty years of compatibility later, the convention persists under the OSStatus name.
Finder gave me a code not listed here, what now? Search the exact number with the word 'OSStatus', Apple's documentation and developer forums use that term. Many unlisted codes are app-specific rather than system codes.
Does -36 mean my drive is dying? It means an I/O operation failed, which is a symptom with several causes (one corrupt file, a bad cable on an external drive, filesystem damage, or real hardware failure). Isolate first, back up immediately, then judge.