What is /private/var/db/diagnostics on Mac? Can you delete it?

Where it is

What it is

Since macOS Sierra, the system and most apps write their log messages to one unified log. The compressed log files are kept in /private/var/db/diagnostics, and a companion folder, /private/var/db/uuidtext, holds the text needed to turn them back into readable messages. The Console app and the log command read from both.

macOS manages the size. Old entries are removed as new ones arrive, so the folder stays within a limit instead of growing without end.

It can be larger than usual when one app or system process is logging heavily, which normally points to a problem with that app.

How big it gets

Usually from a few hundred MB to a few GB, and it levels off because macOS removes the oldest entries.

How to shrink it the right way

1. Run the command below to see how much space the log store takes. It asks for your password because the folders are readable only by the system, and it only reads sizes.
2. If the figure is unusually large, open Console, select your Mac and click Start to see which process is writing most of the messages. Updating or removing that app is the real fix.
3. Restart your Mac. This does not empty the log, but it stops a process that was stuck writing to it.
4. Leave the files in place. The log tool has an erase command, but it removes the history you or Apple Support would need to diagnose a problem, and the space fills again.

sudo du -sh /private/var/db/diagnostics /private/var/db/uuidtext

What happens afterwards

Nothing to expect, since the right action is to leave it. macOS keeps trimming the oldest entries by itself.

How Diskzy handles it

Diskzy's System Data view shows logs as a named part with their size. System logs like these are left to macOS, while the logs in ~/Library/Logs are listed in the Clean up tab.

Related guides

• Logs~/Library/Logs
• DiagnosticReports~/Library/Logs/DiagnosticReports
• /private/var/folders/private/var/folders