Why is my Mac slow? A six-point checklist, in the order worth checking

"My Mac is slow" is a symptom, not a diagnosis. In our experience it nearly always comes down to one of six causes, and checking them in the right order saves you from the most common mistake: cleaning junk off a disk that was never the problem.

Here they are, in the order worth checking, with where each one shows up in our apps and what to do about it.

1. Memory pressure

The first thing to look at is memory, but not how much is "used". macOS deliberately fills spare memory with caches, so a Mac showing 7 of 8 GB used can be perfectly happy. The number that matters is memory pressure, which macOS calculates itself. When it is high, the system is compressing memory and swapping it to disk, and that is the sluggishness you feel when switching apps.

Where to see it: SweepyMac's Mac Health raises "memory under pressure" as a recommendation. Stackyard shows pressure in its Memory section and adds ⚠︎ to its menu-bar item when it is high.

What to do: find the app holding the most. Stackyard groups each app's helper processes under it, so a browser with forty helpers is one row with one number, and the row has a Quit button. Usually the culprit is a browser with too many tabs, a virtual machine, or Docker.

2. One process using the processor

If memory is fine but the Mac is hot, loud and slow, something is busy. A runaway process, a sync client stuck in a loop, or an indexer chewing through a folder you just unpacked.

Where to see it: Stackyard's Vitals lists the top apps by CPU with their energy impact, and the thermal state. SweepyMac's Performance module shows live CPU and load, refreshed every three seconds.

What to do: if the top app is one you do not need right now, quit it. If it is something you do need, give it a few minutes: indexing and first syncs finish.

3. A nearly full disk

A Mac with a nearly full startup disk slows down in ways that look unrelated: apps take longer to open, updates fail, and when memory runs short the system has less room to swap to. This is the one case where cleaning really does make a Mac faster.

Where to see it: SweepyMac's health check flags the disk as almost full at 90 percent used or under 8 GB free, whichever comes first, and the storage gauge at the bottom of its sidebar shows it at all times.

What to do: see the post on what to do when the disk is almost full, which puts the fixes in the order that frees the most for the least risk.

4. Too much starting at login

Every updater, helper and sync service that starts at login takes a little memory and a little processor time, all day. One is nothing. Thirty is a Mac that is slow from the moment you sign in.

Where to see it: SweepyMac's health check warns when there are too many login items, and its Performance module lists the launch agents in your Library. Stackyard's Startup tab shows the same agents with the app each belongs to and whether it is running right now.

What to do: disable the ones for apps you no longer use. In SweepyMac that moves the agent's file to the Trash, restorable with Undo. The post on login items and maintenance covers the rest.

5. Weeks without a restart

Macs are good at running for weeks, but long uptime lets small leaks and stuck processes add up. A restart clears them all at once, and it costs two minutes.

Where to see it: SweepyMac's health check recommends a restart after 14 days of uptime. Its Performance module shows uptime on the live system card.

What to do: restart. If memory climbs back up within a day, the leak is in a particular app, which leads to the last item.

6. Dev processes nobody is watching

If you write code, check this one earlier. Closing a terminal tab does not always stop the dev server inside it, and AI coding agents start servers and watchers of their own. A week later you can have half a dozen node processes holding memory and keeping file watchers spinning on projects you are not working on.

Where to see it: Stackyard's Orphans filter, which shows each one with the tool that started it, the folder it was started in and its PID.

What to do: Quit All, or quit them one at a time if one is something you still want. Stackyard's Guard can also quit orphans automatically after 15 minutes, 30 minutes or an hour, leaving databases like Postgres and Redis alone. The orphans post explains how it decides.

The short version

Check memory pressure first, then what is using the processor, then the disk. Most slow Macs are one of those three. SweepyMac's Mac Health score checks memory, storage, login items and uptime in one place, which makes it a good starting point. If you are a developer, open Stackyard's menu first: memory, the heaviest apps and the orphans are all in it.