Install and run

Caliper runs on macOS 14 or later.

Download

Take the disk image from the releases page, open it, and drag Caliper into Applications. Releases are signed with a Developer ID and notarised by Apple, so they open like any other downloaded app.

With Homebrew

brew install --cask hossainalhaidari/tap/caliper

That taps hossainalhaidari/homebrew-tap, trusts the Caliper cask in it — naming it in full is what Homebrew takes as your say-so — and installs the same signed, notarised disk image as the releases page. The copy keeps itself up to date as any other does (Updates and login), so brew upgrade leaves it alone; brew upgrade --greedy moves it on anyway. brew uninstall --zap --cask caliper removes your widgets and settings along with it — everything listed in Files and uninstalling.

First launch

Caliper has no Dock icon and no window of its own. It starts with one widget, Overview, in the menu bar:

Cell	Shows
CPU 23%	Total processor load, as a number
a small graph	The same, over the last 60 seconds
a ring	Memory used — coloured by memory pressure, not by how full it is (why)
two stacked rates	Download over upload

Click a cell for the detail panel. Right-click (or Control-click) any Caliper item for its menu:

Item	Does
Edit Widgets… ⌘,	Opens the editor
Launch at Login	Starts Caliper when you log in
Check for Updates…	Looks for a new version now — see Updates and login
Check Automatically	The daily update check, on by default
About Caliper	The version and build that is running, with links to the source and to this site’s Privacy page
Quit Caliper ⌘Q	Quits

Everything else, including the look of the menu bar, is in the editor.

No permission is asked for. The one prompt you may see is macOS asking whether Caliper can send notifications, the first time an alert fires.

Build it from source

With Xcode’s toolchain installed, and nothing else:

make app        # build build/Caliper.app and launch it
make install    # copy it to /Applications
make test       # run the test suite
make help       # everything else

make stop quits a running copy. make run is the fastest loop — swift run Caliper, with no bundle — and the menu bar strip it shows is the real thing. What a bundle-less binary cannot do is anything keyed to a bundle identifier: it has no update feed and no login item, so both are left out of its menu, and its alerts go to the system log instead of Notification Center.

A copy you build yourself is a development build: it carries a placeholder version and no update feed, so it never offers to replace itself with the published release.

Signing

Tools/bundle.sh signs with the first Developer ID Application certificate it finds in your keychain (or the one named by $CALIPER_SIGN_IDENTITY), or ad hoc when there is none, and says which it did. The two are very different apps:

Signature	Runs on the Mac that built it	Runs on any other Mac
Developer ID + notarised	yes	yes
Developer ID, not notarised	yes	only past an explicit override
ad hoc	yes	only past an explicit override

For your own Mac, ad hoc is fine. To give a copy to anyone else, see Releasing.