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CaliperCaliper

Overview

Caliper is a system monitor for the macOS menu bar. You build widgets — rows of numbers, graphs and gauges — and each one becomes its own menu bar item, or sits on the desktop. They stay in the menu bar’s own colours until a reading crosses a line you set.

It collects nothing and sends nothing about you: everything it measures stays on your Mac, and the only request it makes is a daily update check you can turn off. Privacy says exactly what that request carries.

Build what you want to see

CPU, cores, memory, network, disks, GPU, temperatures, fans, power, battery and a clock, drawn as numbers, graphs, donuts, dials, bars or a core matrix.

Quiet until it matters

Monochrome by default. Past a threshold a cell turns orange or red, is underlined, and — once the breach has lasted 30 seconds — sends one notification.

Glance, then look

Click a cell and a panel opens on that metric: its last minute, what it is made of, and the processes behind it.

Share a widget

Export one as a .caliperwidget file. Opening one previews it against your own Mac before anything reaches your menu bar.

Start here

Section titled “Start here”
Install and runDownload it or build it, and what you see on first launch.
Widgets and the editorAdding, arranging, renaming and hiding widgets and their cells.
Cell stylesThe nine ways to draw a reading, and which metrics each will take.
AlertsThresholds, the colours and lines they bring, and the notifications.

What it does not do

Section titled “What it does not do”
  • It is not sandboxed, and cannot be: temperatures, fans and power come from interfaces the App Store sandbox blocks. It is distributed as a signed, notarised download instead.
  • It never writes to the hardware. The fan code can read the SMC and nothing else.
  • It does not use WidgetKit for desktop widgets. WidgetKit cannot update every second.
  • It does not colour the menu bar for decoration. Colour means a threshold was crossed.

Conventions in these docs

Section titled “Conventions in these docs”

Menu paths are written the way macOS writes them: System Settings ▸ General ▸ Login Items. Anything in monospace is a literal — a metric id, a file, a command. A metric id like cpu.usage.total is the name a reading has in widget files; Sensors and metrics lists them.