The short answer. Stats is the right default: it is open source, free, and covers the essentials in the menu bar without asking for money or attention. iStat Menus is worth the one-time purchase if you want depth — sensors, fan control, rule-based notifications — rather than a glanceable readout. AirStats is the lightweight option if you also want a desktop widget. AlDente is a different tool entirely: it limits how far your battery charges, which is a battery-health job rather than a monitoring one, so do not pick it expecting a dashboard.
This guide covers 5 system monitors for macOS. Every fact below is drawn from the same verified records that back each app’s own page. The recommendations are our editorial judgment, not payment. Last verified 2026-10-05.
Quick comparison
| App | What it is | Pricing | Licence | Version |
|---|---|---|---|---|
| AirStats | system monitor | Open source | MIT | 1.5 |
| AlDente | battery and power utility | Open source | not published | 1.39.4 |
| Bye AppQuit | system monitor | Open source | GPL-3.0 | 1.0 |
| iStat Menus | system monitor | One-time purchase | not published | 7.50.1 |
| stats | system monitor | Open source | MIT | 3.0.20 |
What actually decides this
- What you are actually monitoring. A general monitor, a battery charge limiter and a fan controller are three products that get shelved together. Name the reading you want before comparing interfaces.
- Menu bar footprint. A monitor lives in the most contested strip of screen you own. How many items it adds, and whether they can be condensed, decides whether you keep it running after the novelty fades.
- Depth on demand. The difference between a useful monitor and a distracting one is whether the menu bar shows a glance and a click reveals the detail, or whether the detail is always in your face.
- Hardware sensors and their limits. Temperature, fan and power readings come from sensors whose availability varies by Mac model. A tool that shows a value on one machine may show nothing on another, and that is the hardware, not the app.
- The observer’s own cost. A monitor that polls aggressively to be accurate uses the resources it is reporting on. The lighter the tool, the less it distorts the picture it draws.
Our picks
- stats — It is MIT-licensed and puts the core readings in the menu bar, which is the whole job for most people. Choose it when you want a free, open-source monitor covering the essentials.
- iStat Menus — It covers CPU, GPU, memory, disks, network, sensors, battery and more, with rule-based notifications and fan control, which is more than a glanceable readout. Choose it when you want depth — sensors, fan control and notifications — and will pay once.
- AirStats — It is a lightweight open-source monitor for CPU, GPU, memory, network, disk, battery and temperature, and it offers a widget alongside the menu bar. Choose it when you want something light with a desktop widget as well as a menu bar item.
- AlDente — It limits how far the battery charges, which addresses long-term wear; it is not a dashboard and should not be chosen as one. Choose it when your goal is battery health rather than monitoring.
The apps
AirStats
AirStats is a system monitor for macOS. Lightweight menu bar system monitor for CPU, GPU, memory, network, disk, battery, and temperature, with a desktop widget. It is released under MIT.
What it does. A menu bar system monitor for macOS. CPU, memory, GPU, network, disk, battery and thermals at 0.046% CPU.
AirStats is listed with current version 1.5.
Full profile and verified facts for AirStats →
AlDente
AlDente is a battery and power utility for macOS. Battery charge limiter for MacBooks. It is open source.
What it does. Menubar Tool to set Charge Limits and Prolong Battery Lifespan - AppHouseKitchen/AlDente-Battery_Care_and_Monitoring.
AlDente is listed with current version 1.39.4.
Full profile and verified facts for AlDente →
Bye AppQuit
Bye AppQuit is a system monitor for macOS. A minimal menu bar app to quickly view and kill running processes. It is released under GPL-3.0.
What it does. Native & Lightweight: Built using modern SwiftUI for a minimal footprint and near-zero CPU usage when idle. Instant Quitting: Quit all running user applications with a single click. Selective Control: Easily click to select or deselect specific apps you need to keep open. Adaptive Design: Features a glass-morphic interface that seamlessly adapts to Light and Dark Mode.
Bye AppQuit is listed with current version 1.0.
Full profile and verified facts for Bye AppQuit →
iStat Menus
iStat Menus is a system monitor for macOS. Menu bar system monitor for macOS covering CPU, GPU, memory, disks, network, sensors, battery and weather, with rule-based notifications and fan control. It is one-time purchase.
Strengths. According to the developer, covers CPU, GPU, memory, disks, network, sensors, battery and weather from the menu bar. Rules can notify on a wide range of events, including a changed public IP, a dropped connection, sustained high CPU or low disk space. Fan speeds can be controlled and ramped gradually based on temperature and battery state.
Trade-offs. Closed source, so the monitoring implementation cannot be independently verified. The vendor’s own one-time price is not published in the sources Nuanyue tracks, so the cost has to be confirmed at purchase. Requires macOS 11 or later. Some readings, such as GPU details and certain sensors, are only available on supported Macs. Apple Silicon support is inferred from the mention of efficiency and performance cores rather than stated explicitly on the pages checked.
Not for. Anyone who wants an open-source monitoring tool they can inspect — iStat Menus is closed source. Users on macOS 10.15 or earlier, since the current version requires macOS 11 or later.
What it does. Menu bar items for CPU, GPU, memory, disks, network, sensors, battery and weather. Per-core CPU usage, history graphs, load averages and CPU frequency. Efficiency and performance cores can be styled differently. GPU processor, memory, temperature and frequency on supported Macs.
iStat Menus is listed with current version 7.50.1.
Full profile and verified facts for iStat Menus →
stats
stats is a system monitor for macOS. free Mac system monitor for the menubar. It is released under MIT.
Strengths. Open source under the MIT licence, with the full source published on GitHub. Free to download and use, with no ads, tracking or subscriptions. Installs directly as a .dmg, via Homebrew, or through an SSH script for headless remote monitoring.
Trade-offs. Developed and maintained by a single person; the README states unsolicited pull requests are generally not accepted, so outside contributions are limited. The README lists the fan-control module as no longer maintained. macOS 12 Monterey or later is required, and beta versions of macOS are not supported. Remote monitoring is handled by the separate System Stats service, which is not the free app.
Not for. Windows or Linux users — Stats is a macOS menu bar app. Anyone who needs working fan control — the README lists the fan-control module as no longer maintained. People who want to contribute code — the README states unsolicited pull requests are generally not accepted.
What it does. CPU, GPU, memory, disk and network monitoring in the menu bar. Hardware sensors: temperature, voltage, power and fan speed. Battery level, health, cycle count and power source. Battery levels of connected Bluetooth devices.
stats is listed with current version 3.0.20.
Full profile and verified facts for stats →
How to choose
- No licence fee, source available. AirStats, AlDente, Bye AppQuit and stats — the source can be read and, under the terms of each licence, reused.
- One-time purchase. iStat Menus — you pay once.
Open source: AirStats, AlDente, Bye AppQuit and stats (4 of 5).
Common mistakes
- Confusing a battery charge limiter with a system monitor. AlDente changes charging behaviour; it does not chart your CPU.
- Watching CPU percentage and drawing conclusions from momentary spikes. Short bursts are normal and the number on screen is a sample, not a verdict.
- Assuming every reading is available on every Mac. Sensor support varies by model, and a missing value is the hardware rather than the app failing.
- Running a heavy monitor on a machine that is already slow. The tool adds load to the thing it is measuring.
How this guide was put together
Each app’s facts come from its own record: the developer’s own pages and repository, the App Store listing where one exists, and the documentation, each with a source grade and an access date. Where a fact rests on the developer’s own statement rather than on something we verified independently, the sentence says so. Where our data has no value for something, the guide says “not published” instead of guessing.
A price appears here only where the record carries one from a stated source; the guide never estimates one, and it records the pricing model alongside so the two can be read together. Prices change and vary by region, so each app links to its own page for the current detail.
The facts and the recommendations are kept apart on purpose. Everything in the app entries, the comparison table and the answers above is composed from the records. The short answer, the criteria and the picks are our editorial judgment: they reflect what we would choose and why, and they are not paid for. Where we make a recommendation we name the condition it applies under, because we do not call anything “the best” without explaining the criteria.
Verified 2026-10-05.
Frequently Asked Questions
How do I choose between these system monitors?
There is no single answer — it depends on what you need. This guide covers 5 system monitors: AirStats, AlDente, Bye AppQuit, iStat Menus and stats. They differ mainly in pricing model, licence and the trade-offs each one carries. Pick by the trade-off you care about rather than by rank.
Are these system monitors free?
Pricing across this group: open source (AirStats, AlDente, Bye AppQuit and stats) and one-time purchase (iStat Menus). We quote a price only where the record carries one from a stated source, and we never estimate one. Prices change and vary by region and by store, so always check the developer’s own page for the current figure.
Which of these system monitors are open source?
AirStats (MIT), AlDente (not published), Bye AppQuit (GPL-3.0) and stats (MIT) are open source.
Do these system monitors support Apple Silicon?
Apple Silicon support is explicitly stated for iStat Menus and stats. For the others our data does not carry an explicit statement either way, so we do not infer one.
How do I choose between them?
Start with how you pay: the guide groups these apps by pricing model, because the budget is the constraint most people actually have. Then check the trade-offs listed for each app: the limitations are the part that decides most people’s choice, because they describe what the app will not do for you.
Who should not use these apps?
iStat Menus and stats each list an audience they are explicitly not aimed at. Those notes come from the same verified records as the rest of this guide, and they are worth reading before you install anything.
When was this data last verified?
The facts in this guide were last confirmed on 2026-10-05. Every app page carries its own verification dates and source list, so you can check any individual claim.
