How to show seconds in the Mac menu-bar clock

Updated 2026 · 3 min read

The default macOS clock shows hours and minutes. If you time things to the second — build runs, download speeds, how long a video call has been going — the missing seconds counter is a small but constant annoyance. One toggle in Clock Options fixes it.

Where to find it in System Settings

Open System Settings (Apple menu → System Settings).
Click Control Center in the sidebar.
Scroll to Clock and click Clock Options…
Turn on Display the time with seconds.

The clock in your menu bar updates immediately to show HH:MM:SS.

The Terminal command

Open Terminal (Applications → Utilities) and run:

# show seconds in the menu-bar clock
defaults write com.apple.menuextra.clock ShowSeconds -bool true
killall SystemUIServer

On macOS 13 Ventura and later, if the above doesn't take effect, also try the integer form:

# alternative for macOS 13+ if the bool form doesn't stick
defaults write com.apple.menuextra.clock ShowSeconds 1
killall SystemUIServer

To go back to the default HH:MM display:

# undo — hide seconds
defaults write com.apple.menuextra.clock ShowSeconds -bool false
killall SystemUIServer

Why it's useful

The most common use cases are precise timing (you can glance at the clock instead of running a stopwatch), watching background processes (does this compile finish in under a minute or not), and log correlation — when you're matching something that happened in a terminal to a timestamp in a log file, seconds matter. It's also just satisfying to have a clock that tells you the full time.

Do it in one click

Mainspring turns this exact setting — and 90+ others macOS buries in Terminal — into a single labelled toggle. Flip Show seconds in clock on, and flip it back just as fast. No commands to memorize, nothing permanent.

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Does showing seconds affect performance?

Technically, yes — a tiny bit. The menu bar redraws the clock every second instead of every minute. On any Mac made in the last decade you won't notice it, and it doesn't show up in Activity Monitor in any meaningful way. The concern occasionally shows up in forum threads, but in practice it's not worth thinking about. If you're on an older Mac that's already struggling, it's one of the last things to blame.

Can I show seconds and 24-hour time together?

Yes. Both settings are independent. Enable 24-hour time in System Settings → General → Language & Region → 24-Hour Time, and enable seconds in Clock Options as above. They stack cleanly — you'll get a clock like 14:32:08.