What's actually happening in there?

CPU — the brain

Your Mac's processor runs every piece of code on your machine. Each app, background service, and system task takes a slice of CPU time. When something is using a lot of CPU, your fan spins faster because the chip is generating heat.

Modern Macs have multiple cores — each core can work on a different task at the same time. SysXray shows you usage per core so you can see if one core is maxed out while others are idle (a sign one process is hogging a single thread).

Memory — the workspace

RAM is your Mac's short-term workspace. Every open app loads its data here. When RAM fills up, macOS starts using swap — borrowing space from your SSD to act as extra memory. This is much slower than real RAM, which is why a full Mac feels sluggish.

macOS uses a concept called memory pressure. Green means you have headroom. Yellow means things are getting tight. Red means macOS is actively swapping and performance will suffer.

Processes — everything that's running

A process is any program running on your Mac — visible apps like Safari, and invisible background tasks like software updaters, cloud sync clients, and system utilities. At any moment your Mac is typically running 300–500 processes simultaneously.

Most are harmless and use near-zero resources. But some go rogue — a browser tab with bad JavaScript, a stuck update process, a sync client scanning millions of files. SysXray shows you the full list sorted by CPU and memory so the culprit is immediately obvious.

Disk — storage and speed

Modern Macs use SSDs that are extremely fast compared to old hard drives — but they can still become a bottleneck. High disk activity (lots of reads and writes) typically means macOS is swapping memory to disk, a backup is running, Spotlight is indexing, or a sync client is working through a large batch of files.

SysXray shows you disk read and write speeds in real time and how full each drive is. If your Mac feels slow and disk activity is high, you now know why.

Thermal — heat and fans

Your Mac's fans exist for one reason: to keep the CPU and GPU below their thermal limits. When a chip gets hot it throttles itself — it deliberately runs slower to reduce heat. This is why a hot Mac feels slow even if the CPU meter shows 100% usage.

macOS reports a thermal pressure level — Nominal, Moderate, Heavy, or Critical. SysXray displays this alongside the CPU temperature and fan speed so you can see exactly when your Mac starts throttling and why.

Background services — what starts with your Mac

macOS uses a system called launchd to manage background services. There are three types:

Network — connections and ports

Every app that talks to the internet opens a network port — a numbered channel for sending and receiving data. SysXray shows you every open port and active connection on your Mac, including which process opened it.

This is useful for spotting unexpected connections — a process phoning home that shouldn't be, or a development server you forgot to stop. It's also the fastest way to find what's eating your bandwidth.