# Why is my Mac so slow? How to find the cause, and fix it

Canonical page: https://vitalsmac.com/why-is-my-mac-so-slow

By Atta Ur Rehman Shah, maker of Vitals. Published September 30, 2026.

**Short answer:** A slow Mac almost always has one cause you can see. Open Activity Monitor: sort the CPU tab by % CPU to find an app that never rests, and check Memory Pressure on the Memory tab to see whether the Mac is short of memory. Then check free space in System Settings → General → Storage, and whether the fans are loud. After a macOS update, Spotlight and Photos slow a Mac for a day or two. Vitals, a system monitor for the Mac, shows which app was busy when the Mac was slow, over the last hours or 30 days, and tells you when an app misbehaves.

## How to find what is slowing your Mac down

1. Open Activity Monitor (press ⌘Space and type its name). Click CPU and sort by % CPU. An app near the top while you are not using it is the first suspect.
2. Look at Idle at the bottom of the CPU tab. Near zero means the CPU is the bottleneck. If Idle is high while the Mac feels slow, the cause is elsewhere.
3. Click Memory and look at Memory Pressure at the bottom. Yellow or red means the Mac is short of memory for what is open.
4. Click Disk and sort by Bytes Written. A backup, a sync or indexing writing heavily slows everything that reads or writes files.
5. Open System Settings → General → Storage. A disk that is nearly full leaves macOS little room for swap, caches and updates.
6. If one app shows a spinning beach ball while the rest of the Mac is fine, the problem is that app, not the Mac.

Restart when memory pressure stays red after you quit the apps that caused it, or when a process is stuck and Force Quit does not end it. A restart does not fix causes that come back, so find those first.

A Mac slows down when one resource runs out: the CPU, memory, the disk, or the room to stay cool. Each leaves a different trace in Activity Monitor and System Settings, and each has its own fix, which is why general tips so often miss. The table below matches what you notice to the likely cause and where to look, and the sections after it link to a full guide for each.

## What slows a Mac down

| What you notice | Likely cause | Where to check |
|---|---|---|
| Slow all the time, fans on or the case warm | An app keeping the CPU busy | Activity Monitor → CPU, sorted by % CPU |
| Slow with many apps or tabs open, or when switching apps | The Mac is short of memory | Activity Monitor → Memory: Memory Pressure |
| Slow for a day or two after a macOS update | Spotlight and Photos catching up | Activity Monitor → CPU: mds_stores, photoanalysisd, mediaanalysisd |
| Slow and hot, with kernel_task near the top | Heat: macOS is holding the CPU back | Airflow, the room, and the app next in the list |
| Slow to save, open files and install updates | A disk that is nearly full | System Settings → General → Storage |
| Slow for minutes after you log in | Too many apps opening at login | System Settings → General → Login Items & Extensions |
| A spinning beach ball in one app | That app is not responding | Activity Monitor: the app shown as Not Responding |

## Is it the Mac, or one app?

Start by telling the two apart. If one app shows the [spinning beach ball](https://vitalsmac.com/glossary/spinning-wait-cursor) while other apps switch and scroll normally, that app is stuck, and Activity Monitor lists it as [Not Responding](https://vitalsmac.com/glossary/not-responding). Give it a minute, then force quit it with ⌥⌘Esc if it does not recover.

If everything is slow, from typing to switching windows, the Mac as a whole is short of something. The steps above find what.

## CPU: an app that never rests

A browser tab running a script, a sync that keeps retrying, a build that never finished: one busy process can make the whole Mac feel slow. Sort Activity Monitor’s CPU tab by [% CPU](https://vitalsmac.com/glossary/cpu-percent) and look for a row that stays high while you are not using its app. [How to check CPU and memory usage](https://vitalsmac.com/check-cpu-memory-usage-mac) goes through the figures step by step.

## Memory: when the Mac runs short

Memory Used near the total is normal. [Memory Pressure](https://vitalsmac.com/glossary/memory-pressure) is the figure that matters: when it turns yellow or red, macOS is compressing memory and moving it to disk, and every switch between apps waits for it. [How to free up RAM on a Mac](https://vitalsmac.com/free-up-ram-mac) covers what to quit and what does not help, and [Chrome using too much memory](https://vitalsmac.com/chrome-using-too-much-memory-mac) covers the usual biggest user.

## Storage: a disk that is nearly full

macOS needs free space to work: for swap when memory runs short, for caches, and to download and install updates. When the disk is nearly full, everything that writes has to wait for space to be found. Check System Settings → General → Storage, and remember that the free figure includes [purgeable space](https://vitalsmac.com/glossary/purgeable-space) macOS has not freed yet. If [System Data](https://vitalsmac.com/glossary/system-data) is the largest part, its entry shows how to find what is in it.

## Heat: a Mac that slows itself down

When the chip gets too hot, macOS slows it down to cool it. That is [thermal throttling](https://vitalsmac.com/glossary/thermal-throttling), and [kernel_task](https://vitalsmac.com/glossary/kernel-task) high in the CPU list is the sign. The fix is to find the app heating the Mac, and to check the airflow around it. [Why are my Mac’s fans so loud](https://vitalsmac.com/mac-fan-loud) covers both.

## After an update, and at login

After a macOS update, [Spotlight](https://vitalsmac.com/glossary/spotlight-indexing) re-indexes the disk and Photos analyzes your library again. The Mac is slower for a day or two, and faster once they finish. Leaving it on power for a few hours lets them finish sooner.

A Mac that is slow for minutes after you log in is usually opening too much at once. System Settings → General → Login Items & Extensions lists the apps under Open at Login, and the background items apps add. Remove what you do not need at login; you can still open it when you do.

## How to speed up a slow Mac

Once you know the cause, the fix follows from it. In the order that helps most often:

1. Quit or update the app keeping the CPU busy, or close the browser tab behind it. [How to check CPU and memory usage](https://vitalsmac.com/check-cpu-memory-usage-mac) shows how to find it.
2. Close what is using the memory when Memory Pressure is yellow or red. [How to free up RAM](https://vitalsmac.com/free-up-ram-mac) covers what to quit first.
3. Free disk space when the disk is nearly full, starting with the largest items in System Settings → General → Storage.
4. After a macOS update, leave the Mac on power for a few hours so Spotlight and Photos can finish.
5. Remove apps you do not need from Open at Login, in System Settings → General → Login Items & Extensions.
6. Keep it cool: a hard surface, clear vents, and no heavy work in direct sun. See [why a Mac’s fans get loud](https://vitalsmac.com/mac-fan-loud).
7. Install updates for macOS and your apps. Many slowdowns are bugs that updates fix.
8. Restart when memory pressure stays red after you quit the apps that caused it.

## What does not speed up a Mac

Most of the usual advice treats symptoms that come back.

- Cleaner and RAM booster apps. They delete caches macOS rebuilds and push out memory that apps ask for again, so the Mac is slower until both are back.
- Restarting every day. It hides an app that leaks or gets stuck for a few hours, and then the slowdown returns. Find the app instead.
- Reinstalling macOS as a first step. It rarely fixes what the steps above find, and it takes an afternoon.

## What Vitals adds

Vitals shows which app is behind a slow Mac, and when.

- About 60 apps instead of about 1,000 processes, each with its helper processes counted in
- 30 days of CPU, memory, disk, network and energy for every app, ranked over the last hour, 12 or 24 hours, 7 or 30 days, so a Mac that was slow this morning has a name next to it
- A notification when a background app keeps the CPU busy, keeps growing in memory, or hammers the disk or the network, and when the Mac runs short of memory
- Keeping the Fans On names the apps heating the Mac, with Quit beside each

Good to know:

- Root and system processes, such as kernel_task and WindowServer, are measured when the optional helper is on.
- Vitals does not clean or delete anything. It shows which app is the cause, and quits it after asking.

Vitals is $9 during the launch, $29 after it, once: [vitalsmac.com](https://vitalsmac.com/).

## Questions people ask

### Why is my Mac so slow all of a sudden?

Something changed: an app or a browser tab stuck at high CPU, a macOS update that set off indexing, memory running short with more open than usual, or a disk that has filled up. Activity Monitor’s CPU and Memory tabs show the first three, and System Settings → General → Storage the last.

### How do I speed up my Mac?

Find the one thing slowing it down and deal with that: quit the app keeping the CPU busy, close what is using the memory, free disk space, or let indexing finish. General tweaks and cleaner apps help far less.

### Does restarting a Mac make it faster?

For a while, when an app or system process is leaking memory or stuck. If the Mac is slow again a day later, the cause is still there, and Activity Monitor will show it.

### Do Mac cleaner apps make it faster?

No. Most delete caches macOS rebuilds, or push out memory that apps ask for again. The Mac is slower until both are back.

### Why is my Mac slow after an update?

Spotlight is re-indexing the disk and Photos is analyzing your library again. Both finish on their own within a day or two; leave the Mac on power to let them finish sooner.

### Is there an app that shows why my Mac is slow?

Vitals shows which app is using the CPU, memory, disk and network, one row per app with its helpers counted in, and keeps 30 days of it, so you can see which app was busy when the Mac slowed down. It also sends a notification when an app misbehaves.

In the glossary: [Spinning wait cursor](https://vitalsmac.com/glossary/spinning-wait-cursor), [Not Responding](https://vitalsmac.com/glossary/not-responding), [Memory pressure](https://vitalsmac.com/glossary/memory-pressure), [% CPU](https://vitalsmac.com/glossary/cpu-percent), [kernel_task](https://vitalsmac.com/glossary/kernel-task), [mds_stores and mdworker](https://vitalsmac.com/glossary/spotlight-indexing), [System Data](https://vitalsmac.com/glossary/system-data), [Uptime](https://vitalsmac.com/glossary/uptime).

More guides: [What’s draining my Mac’s battery](https://vitalsmac.com/mac-battery-draining-fast), [Which app is using my CPU or memory](https://vitalsmac.com/check-cpu-memory-usage-mac), [Why won’t my Mac sleep](https://vitalsmac.com/mac-wont-sleep), [Chrome using too much memory](https://vitalsmac.com/chrome-using-too-much-memory-mac), [Why are my Mac’s fans so loud](https://vitalsmac.com/mac-fan-loud), [How to control fan speed on a Mac](https://vitalsmac.com/mac-fan-control), [How to free up RAM on a Mac](https://vitalsmac.com/free-up-ram-mac), [Docker using too much memory](https://vitalsmac.com/docker-using-too-much-memory-mac), [How to stop Docker containers](https://vitalsmac.com/stop-docker-containers-mac), [Volume mixer for Mac](https://vitalsmac.com/mac-volume-mixer), [Activity Monitor alternatives](https://vitalsmac.com/best-activity-monitor-alternatives), [iStat Menus alternatives](https://vitalsmac.com/best-istat-menus-alternatives), [Stats alternatives](https://vitalsmac.com/best-stats-alternatives), [Task Manager for Mac](https://vitalsmac.com/task-manager-for-mac), [Best system monitors for Mac](https://vitalsmac.com/best-system-monitor-for-mac), [Best menu bar monitors for Mac](https://vitalsmac.com/best-menu-bar-system-monitor-for-mac), [Best volume mixers for Mac](https://vitalsmac.com/best-volume-mixer-for-mac).