Does a system monitor slow the Mac down?

A little, and how much depends on how often it reads and how much it draws. The honest way to find out is Activity Monitor on your own machine after a day of use.

Can these read temperature and fans on Apple silicon?

Many can, through the sensors the system exposes. What is available differs by model and by macOS version, so what a developer states for their own app is better than a general answer.

What is a menu bar app?

An app that lives in the strip along the top of the screen instead of the Dock. It has an icon there, and clicking it drops down a small window. Most have no main window at all, so they stay out of the way until you want them and never appear when you switch apps.

Do menu bar apps slow a Mac down?

Each one is a running process, so a dozen of them is a dozen processes. Most sit idle and cost close to nothing. The ones worth watching are those doing work when you are not looking: reading the screen, polling a server, or watching every file you save. Activity Monitor will tell you which is which on your own machine.

My menu bar is full. What then?

macOS drops icons that no longer fit, and on a Mac with a notch there is less room than there looks. Holding Command and dragging rearranges them, so the ones you use can be kept to the left of the crowd. There are also apps whose whole job is hiding and grouping the rest, listed here under Utilities.

System category

System menu bar apps

System menu bar apps for macOS. 9 listed: 1 free, 3 free with a paid upgrade and 5 paid. Of those, 4 with a free trial. Prices and trials as the developers state them.

9 apps

About MacMetra

MacMetra , also on the App Store , opens the developer's site in a new tab MacMetra is a system monitor that lives in the menu bar of your Mac.

A system monitor that lives entirely in the macOS menu bar — no Dock icon, no main window. One compact item shows CPU load, thermal state and memory; you choose which appear and in what order. Clicking it opens a panel with cards for CPU, memory, storage, thermal state and power. It stays inside the App Sandbox, so it shows the four-step thermal state macOS publishes rather than named sensors in degrees, and no fan speeds. No helper tool, no network access, no accounts, no analytics, no history kept. Swift and SwiftUI, universal, macOS 14 or later.

System 208 views 1 clicks

$2.99
About OpenNavo

OpenNavo, opens the developer's site in a new tab

OpenNavo is a free open-source Homebrew GUI for Mac with a menu-bar system monitor (CPU, memory, temps, fans), ClamAV malware scanning before installs, leftover-aware uninstall, and disk cleanup. Install and update Homebrew apps in one click; no account required.

System 188 views 8 clicks

Free
About Shiny

Shiny, opens the developer's site in a new tab Shiny is the one-tap memory cleanup app for Mac.

Shiny is a menu-bar app for Mac that frees inactive memory and quiets the background apps eating your RAM, so your Mac feels like the day you bought it.

System 162 views 1 clicks

$4.99
About Strata

Strata, opens the developer's site in a new tab Maps your whole drive in seconds. Removes things you can put back. One-time purchase, no subscription.

Mac disk cleaner: see what fills your disk, clear junk, backups and System Data to the Trash. macOS 13+, universal. 14-day free trial, $9.99 once.

System 132 views 1 clicks

$9.99
About Multimeter

Multimeter, opens the developer's site in a new tab

A Mac menu bar app with live meters for battery, CPU, watts, network, timers and your own numbers. Pick a face or build your own. $19.99 once, no subscription.

System 85 views

$19.99
About Amply

Amply, opens the developer's site in a new tab

Holds your MacBook at 80% using the charge limit built into macOS, with no helper or admin password, and says in plain words why it is or isn't charging.

System 45 views 1 clicks

$9.5 14-day trial
About PulseBar System Monitor for Mac

PulseBar System Monitor for Mac, opens the developer's site in a new tab

PulseBar puts live CPU, memory, network, disk, temperatures, and fan speed in your Mac’s menu bar, with history graphs. Native, signed and notarized. One-time $9, no subscription, no account, no telemetry.

System 43 views

Paid
About RAMKeeper

RAMKeeper , also on the App Store , opens the developer's site in a new tab

RAMKeeper is a Mac memory monitor that lives in the menu bar. The free App Store build shows system memory pressure (green / yellow / red) with swap and compressed-memory readings; the free direct download breaks memory down per app and per renderer process and flags hogs such as Chrome helpers, Slack and ChatGPT, with current vs. peak. Pro (one-time purchase) adds threshold rules, Focus Mode to suspend a batch of background apps, and gentle restarts that log the memory macOS actually handed back. No subscription, no ads, no tracking. macOS 12 or later.

System 34 views

$19
About Mac Ninja

Mac Ninja, opens the developer's site in a new tab

Mac Ninja is a menu bar utility that unloads idle browser tabs and lowers the CPU and disk priority of busy background apps. Sleeping tabs stay in the tab bar and reload when selected. The dashboard shows which tabs are asleep and what memory was returned. Seven days free without a card, then $9.99/year or $24.99 lifetime for up to three Macs.

System 22 views 2 clicks

$24.99 7-day trial

What system menu bar apps do

System monitors put what the machine is doing where you can see it: processor, memory, disk, network, temperature, battery. Activity Monitor has all of it and is a window you have to go and open, which is the difference.

The useful moment for this number is while the Mac is slow, not afterwards. In the menu bar you notice the spike; in a window you go looking once it has passed.

9 listed: 1 free, 3 free with a paid upgrade and 5 paid. Of those, 4 with a free trial.

What to compare

What it shows at a glance. A graph, a number, or a colour. More detail in the bar means less room for everything else, and a crowded menu bar is the problem these often create.
How often it reads. A monitor is itself a running process. One that samples every second costs more than one that samples every five, which matters most on a laptop on battery.
Which sensors it needs. Temperature and fan readings need lower-level access than processor and memory. Worth knowing which an app wants before it asks.
Whether it can tell you. Watching a number is a habit. Being told when it passes a line is a feature, and the two are not the same app.

Questions

Does a system monitor slow the Mac down?: A little, and how much depends on how often it reads and how much it draws. The honest way to find out is Activity Monitor on your own machine after a day of use.
Can these read temperature and fans on Apple silicon?: Many can, through the sensors the system exposes. What is available differs by model and by macOS version, so what a developer states for their own app is better than a general answer.
What is a menu bar app?: An app that lives in the strip along the top of the screen instead of the Dock. It has an icon there, and clicking it drops down a small window. Most have no main window at all, so they stay out of the way until you want them and never appear when you switch apps.
Do menu bar apps slow a Mac down?: Each one is a running process, so a dozen of them is a dozen processes. Most sit idle and cost close to nothing. The ones worth watching are those doing work when you are not looking: reading the screen, polling a server, or watching every file you save. Activity Monitor will tell you which is which on your own machine.
My menu bar is full. What then?: macOS drops icons that no longer fit, and on a Mac with a notch there is less room than there looks. Holding Command and dragging rearranges them, so the ones you use can be kept to the left of the crowd. There are also apps whose whole job is hiding and grouping the rest, listed here under Utilities.