Why is my Mac so slow?
By Junaid, maker of Taskglass · Updated
A slow Mac is almost always one of four things: an app using a lot of CPU, more apps than your memory can hold, a nearly full disk, or macOS doing background work such as Spotlight indexing after an update. Open Activity Monitor, sort by % CPU and check the Memory Pressure graph: that finds the cause in about two minutes.
How to find what's slowing your Mac
- 1
Open Activity Monitor
Press ⌘ Space, type Activity Monitor and press Return. It's also in Applications › Utilities.
- 2
Sort by CPU
Click the CPU tab, then the % CPU column header. An app that stays near or above 100% for minutes while you aren't using it is your suspect. Activity Monitor counts 100% per core, so busy apps can show 200% or more.
- 3
Check memory pressure
Click the Memory tab and look at the Memory Pressure graph at the bottom. Green is fine, even when Memory Used looks high. Yellow or red means macOS is compressing memory or swapping to the SSD, and everything slows down.
- 4
Check free disk space
Choose Apple menu › System Settings › General › Storage. macOS needs free space for swap and caches; as a rule of thumb, keep at least 10–20 GB free.
- 5
Quit the culprit, then restart if needed
Quit the busy app with ⌘Q. If it won't respond, press ⌥⌘Esc and force quit it. A restart clears memory and finishes pending updates.
Common causes of a slow Mac
| Cause | How to spot it | What to do |
|---|---|---|
| One app using lots of CPU | High % CPU in Activity Monitor for minutes | Quit or restart that app; close heavy browser tabs |
| Too many apps or tabs open | Memory Pressure is yellow or red | Quit apps you aren't using; restart the browser |
| Spotlight indexing | mds_stores or mdworker busy, often after a macOS update | Wait: it finishes on its own |
| Nearly full disk | Little free space in Storage settings | Delete or move large files |
| Heat | kernel_task high, Mac feels hot | Let it cool; quit heavy apps; use a hard surface |
| Too many login items | Slow after startup, many menu bar icons | Remove items in System Settings › General › Login Items |
What is normal CPU usage on a Mac?
When you aren't doing much, total CPU use is usually low, with a few processes spiking briefly. Activity Monitor counts 100% per core, so a 10-core Mac can show up to 1,000%. One app holding 100% or more for minutes while you're idle is not normal.
Why does my Mac say memory is almost full?
macOS fills spare memory with cached files so apps open faster, so Memory Used is often high on a healthy Mac. Memory pressure is the number that matters: if it stays yellow or red, you're running more than your RAM can hold.
Why is my Mac slow after a macOS update?
After an update, Spotlight re-indexes your files and Photos may re-analyse your library, so mds_stores, mdworker or photoanalysisd can stay busy for hours. It's normal and settles on its own; leave the Mac on and plugged in.
Why is my Mac slow when it's hot?
When the chip gets too hot, macOS slows it down to protect it. Activity Monitor shows this as kernel_task taking a lot of CPU: it's holding other apps back on purpose. Fix the heat and the speed comes back.
Should I use a Mac cleaner app?
Usually not. Most slowdowns come from one app or from memory pressure, which cleaners don't fix, and macOS manages its own caches. Find the cause first.
How Taskglass helps
Taskglass does these checks for you. It groups helper processes under their app, so Chrome is one row with one total; it explains every process in plain English; and it keeps 30 days of history, so you can see what was slowing the Mac an hour ago, not only right now.
See how it worksQuestions
How do I see what's slowing down my Mac?
Open Activity Monitor (press ⌘ Space and type Activity Monitor), click the CPU tab and sort by % CPU. Then check the Memory Pressure graph in the Memory tab.
Does restarting a Mac make it faster?
Often, for a while. A restart clears memory, stops stuck background processes and finishes pending updates. If the Mac slows down again, find the app causing it.
How much free disk space does a Mac need?
There's no exact number, but as a rule of thumb keep at least 10–20 GB free so macOS has room for swap and caches.
Is kernel_task a virus?
No. kernel_task is the core of macOS. High kernel_task CPU usually means your Mac is hot and macOS is slowing things down to cool it.
Processes you might see
- kernel_taskThe core of macOS itself. It also holds busy apps back on purpose to stop your Mac overheating.
- WindowServerDraws every window, menu and animation you see on screen, and routes your clicks and keystrokes.
- mds_storesMaintains Spotlight's search index on disk, updating it as files change.
- mdworkerA Spotlight worker that reads files and extracts searchable details for the index.
- photoanalysisdAnalyses your photos in the background for Memories, People and searching by what's in them.
- Google Chrome Helper (Renderer)Runs web pages and extensions for Chrome; usually one per site or extension.