Mac storage basics · Caches, logs and temporary files
Where are log files on a Mac, and can I delete them?
Short answer: In ~/Library/Logs (including DiagnosticReports) and /Library/Logs. Old app logs and crash reports are safe to delete; leave system logs to macOS, which trims them itself.
Logs and crash reports live mainly in ~/Library/Logs (including DiagnosticReports) and /Library/Logs, plus system logs macOS manages itself. macOS rotates and trims its own logs automatically, so they rarely grow large.
When they do, it's usually one app writing far too much. Deleting an app's old log files is safe; check the newest one first — it often explains what's going wrong.
Leave system log folders to macOS. If logs keep ballooning, update or reinstall the app responsible. Storage Studio's What's Using Space lists crash reports and similar leftovers among its known quick wins.