Native Swift · Menu bar
Free Menu Bar System Monitor for Mac
Worm Cleaner includes a free menu bar system monitor for macOS that shows live CPU load, a memory breakdown, disk capacity and thermal status directly in the menu bar. It is written in native Swift 6 and SwiftUI, sits under 35 MB resident while idle, and is part of an app you may already have installed for cleaning.
By Naman Namdev
Clepsydra Technologies
Updated
Version 1.0.4
Most Mac menu bar monitors are an Electron app in a 40 MB wrapper, and many of them upload usage data as a side effect of being distributed through an analytics-funded model. Activity Monitor itself is excellent and free, but it is a window you have to open and close rather than a persistent glanceable readout.
- CPU — live per-core load and the process count.
- Memory — broken down as App, Wired and Compressed, which is the split that actually tells you whether you have a memory problem.
- Disk — current capacity and total space reclaimed.
- Thermals — thermal and fan status.
- Interaction — left-click for live metrics, right-click for the context menu.
How much memory does it use?
under 35 MB resident on macOS and under 42 MB on Windows, measured while idle. That is measured on the author's machines rather than estimated, and it is the main practical difference from an Electron-based monitor. The App / Wired / Compressed breakdown it displays is a macOS-specific nicety: Wired and Compressed are memory the system cannot simply reclaim on demand, and noticing Compressed climbing is often the first sign that you need more RAM rather than more cleaning.
Lightweight system monitors compared
Free Mac system monitors | Worm Cleaner monitor | Typical Electron monitor | Activity Monitor |
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| Price | Free, MIT | Free or paid | Free, built in |
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| Distribution | Native Swift 6 + SwiftUI | Electron / web wrapper | System binary |
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| Idle memory | Under 35 MB (measured) | 180–450 MB | Varies |
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| Opens in a menu bar | Yes | Yes | No, window only |
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| Memory split App/Wired/Compressed | Yes | Varies | Yes |
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| Thermal and fan status | Yes | Rarely | Yes |
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| Bundled with a cleaner | Yes | Sometimes | No |
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| Source code | Public, MIT | Usually closed | Closed |
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If you only want monitoring and will never clean anything, Activity Monitor is the right answer and costs nothing. Worm's monitor earns its place if you want the readouts and the cleaner in one native app.
Windows equivalent
The Windows build has the same feature in the system tray: CPU via GetSystemTimes, RAM via GlobalMemoryStatusEx, total/free/used space across every mounted NTFS, FAT32 and exFAT volume, top processes by working set, and system facts including edition, build, architecture, core count and uptime. It also runs health checks for disk, memory and CPU with OK / Notice / Action needed. The reclaimed-bytes figure is read back from the audit log, so it only ever reports bytes genuinely removed.
If your menu bar icon is missing after installing, a menu bar manager such as Bartender, Ice or Hidden Bar may be hiding it.
Frequently asked questions
What is the best menu bar system monitor for Mac?
If you want a glanceable persistent readout, a native menu bar monitor is the right category, and the deciding factors are idle memory and whether it has a telemetry story. Worm's is included free with the cleaner, is native Swift, and sits under 35 MB resident while idle. If you do not need cleaning at all, Activity Monitor is built in, free and excellent — it is just a window rather than a menu bar item.
Is there a lightweight system monitor for Windows too?
Yes, in the Windows build of the same app. The system tray panel shows CPU, memory, free disk, uptime and total bytes reclaimed, and a hardware monitor reports CPU utilisation, RAM usage, per-volume space, top processes by working set and system facts, plus OK / Notice / Action needed health checks for disk, memory and CPU.
How much memory does a menu bar monitor use?
Worm's monitor is under 35 MB resident on macOS while idle, measured on the author's machines. Electron-based monitors typically sit between 180 and 450 MB. The gap matters most on an older Mac, where the difference between a native and an Electron app is the difference between noticing and not noticing the monitor.
Does the system monitor send my usage data anywhere?
No. The app has no analytics and makes no network calls during normal operation. The only network call in the macOS app is the optional update check, and it is off until you request it. The Windows build behaves the same way.
Download Worm Cleaner
Worm Cleaner is free, MIT licensed and runs on macOS 14+ and Windows 10/11. No account, no subscription, no telemetry in the app.
