Mister Plimsoll icon

Mister Plimsoll

Disk space monitoring that stays out of your way.

Avoid that too-full drive pressure

Mister Plimsoll is a small menu bar utility for macOS that keeps tabs on whether you are running out of storage on the volumes you choose to monitor. You can get an alert, notification, email, iMessage, or Pushover whenever any one of them gets too full. Set a threshold for each drive — internal, external, Time Machine — and Mister Plimsoll will alert you before you run out of room.

Download Download on the App Store

Version: 1.1.5. Requirements: macOS 14 (Sonoma) or later. Apple Silicon or Intel Mac.

What you get

Mister Plimsoll menu bar dropdown showing last-checked time, Check Now, monitored drives with progress bars, and Settings/Quit
The menu bar dropdown shows live status for every monitored drive.
  • Per-volume thresholds Choose different alert levels for each volume — including startup, backup, and external drives.
  • On-screen alerts Floating notification windows you can dismiss.
  • Daily caps Limit how many times you can be reminded about a single volume per day.
  • Live alerts Send an alert by email, notification, Messages (iMessage), or the Pushover app when a drive crosses the line.
  • Free, no tracking Mister Plimsoll does not track you, require an account, or nag you about tipping.
  • Webhook support You can enter a standard webhook for a service, like Zapier or Slack, or send JSON data to your own endpoint.
  • Stays in the menu bar Click the Plimsoll mark to see status. Optional Dock icon, to reduce clutter.
  • Critical threshold Set a separate threshold for all drives for a critical overfull level alert.
Mister Plimsoll Volumes settings panel showing per-volume monitoring thresholds
You can set thresholds by volume for an alert when storage is getting slim.

For the full walkthrough — schedule, storage policy, per-volume thresholds, and every notification channel — see How to use Mister Plimsoll.

Why “Plimsoll”?

The Plimsoll mark is the load line painted on a ship’s hull — the limit past which you can’t safely add more weight without risking the boat. It’s named for Samuel Plimsoll, the British MP whose 1876 Merchant Shipping Act made it law. The mark is the universal reminder that there is such a thing as too full.

An early example of load lines from Practical Shipbuilding, 1916 (via Wikimedia Commons)

Help

The How to use Mister Plimsoll page covers every feature in detail. To send email alerts you may also need an app-specific password from your email host (Apple, Google, Fastmail, etc.) — there’s a short guide for how to set one up.

Thanks

Thanks to beta testers Michaël Fortin, Joe Kissell, Glen MacDonald, Jason Snell, and Jonathan Whiteland for feedback!