How to Speed Up a Slow Mac

The short answer. A slow Mac is almost never slow for one reason, and the mistake most people make is starting with the fix they have read about rather than with a measurement. Spend two minutes in Activity Monitor and in System Settings, decide which of the four bottlenecks you have, and then apply the one fix that addresses it. In our experience of working through this on a few dozen machines, roughly four cases in five come down to free disk space, a stuck background process, thermal throttling, or a stalled network mount — in that order.

This guide is the diagnostic order we use. It is written for macOS on both Apple Silicon and Intel, and it says where the two differ, because the two generations of hardware fail in different ways.

Start with a measurement, not a fix

Open Activity Monitor (Applications → Utilities, or search with Spotlight) and look at three tabs in this order. Each one rules a cause in or out.

CPU. Sort by % CPU and leave it running for thirty seconds. A healthy idle Mac sits in the low single digits. A single process pinned at 100% or more is your answer, and the fix is that process, not the machine. Pay attention to processes you did not install deliberately: mds, mdworker and mds_stores are Spotlight indexing, photoanalysisd and cloudd are Photos and iCloud, bird is iCloud Drive syncing, and backupd is Time Machine. All of them are legitimate and all of them can run for hours after a large import.

Memory. The Memory Pressure graph at the bottom of the tab is more useful than the “Memory Used” number, and this is the single most misunderstood part of the app. Green means the system has room; yellow means it is compressing and swapping but coping; red means it is spending time moving pages to disk instead of running your work. The percentage next to “Memory Used” includes cached files, which macOS will evict on demand — a Mac showing 14GB of 16GB used with green pressure is not short of memory.

Disk. The Disk tab shows reads and writes per process. Sustained writes of tens of megabytes per second on an idle machine mean something is copying, indexing, syncing or backing up. That is normal after a big download and abnormal a week later.

Then check free space. Apple menu → System Settings → General → Storage. Two numbers matter: how much is free, and how much is purgeable. Purgeable space is data macOS can delete on demand — local Time Machine snapshots, iCloud files not yet downloaded, cached media — and a drive that reports 4GB free with 40GB purgeable is not actually short of space, it is just reserving it.

Cause 1: the startup disk is too full

This is the most common cause and the easiest to fix, but the mechanism is worth understanding because it explains why the symptom is intermittent. APFS writes files copy-on-write: changing a block writes a new block elsewhere and then repoints the metadata. That means every save needs free space for the new copy before the old one is released. When the volume is nearly full, the filesystem has to wait for space to be freed before it can allocate, and every write becomes a round trip. Swap suffers the same way, and once swap cannot grow, memory pressure turns red and the machine starts killing background apps to stay alive.

The practical floor is ten to fifteen percent free. Below that, everything else you do to speed the machine up is fighting the filesystem.

Find what is actually large. Don’t guess at folder sizes in Finder — it reports the logical size and gets slow on big trees. Use a disk-usage analyser that reads the volume directly and draws it as a map. DaisyDisk and GrandPerspective both do this; OmniDiskSweeper gives you a sortable list instead of a map if you prefer numbers. The point is the same: you are looking for the three or four items that account for most of the space, and they are almost always in the same places.

The usual suspects, in order of how much they usually free:

Deleting an app by dragging it to the Trash leaves its container, its launch agents and its caches behind — which is why uninstalling 20GB of apps often frees 6GB. An uninstaller that finds the associated files is worth having for exactly this reason; AppCleaner is the minimal version of that idea and CleanMyMac bundles it with the cache and mail-attachment cleanups. Both are in the Mac cleaner category if you want to compare.

Do not delete caches to free space unless you have to. A cache you delete is a cache the system rebuilds, usually within the hour, at the cost of slower launches and more disk writes. The one exception is a cache that has become corrupt and is causing a specific bug — that is a repair, not a cleanup. There is a longer treatment of the distinction in how to clean cache on Mac, and a list of where the space actually goes in how to free up storage on Mac.

Check for local snapshots before you panic. Time Machine keeps hourly snapshots on the internal drive when it cannot reach its backup disk, and they are invisible in Finder. tmutil listlocalsnapshots / lists them; tmutil deletelocalsnapshots / removes them. They are purgeable, so macOS will delete them itself under pressure, but if your drive shows 60GB of purgeable space and you need it now, this is where it is.

Cause 2: something is running that should not be

A Mac has three layers of “starts automatically”, and people usually check only the first.

Login items. System Settings → General → Login Items lists the apps that open at login, plus two lists most people never open: Allow in the Background, which is where installers register helpers, and Extensions. On Monterey and earlier the same list lives under Users & Groups. Remove anything you do not recognise — the app can still be launched manually, and a login item that turns out to be needed is one click to restore.

Launch agents and daemons. These are the plists in ~/Library/LaunchAgents, /Library/LaunchAgents and /Library/LaunchDaemons. An agent runs as you and can show a UI; a daemon runs as root with no UI and no session. Most third-party software installs at least one, and uninstalling by dragging the app to the Trash leaves them running forever. To see what is actually loaded, sudo launchctl list prints every service with its PID and last exit status; a non-zero exit status on a service that keeps restarting is a process burning CPU in a loop, and it will never show up as a single high-CPU process because it spends its life being relaunched.

The command-line view is ugly but honest. TaskExplorer and KnockKnock present the same information as a browsable list with signing information attached, which is faster than reading plists. There is a step-by-step walkthrough of the whole layer in how to manage login items and startup agents on Mac.

Menu bar apps. Every menu bar item is a running process, and a menu bar with fifteen icons is fifteen processes plus whatever they spawn. iStat Menus and Stats are both worth having and both poll hardware on a timer; that is a real cost, small but not zero. If you are hunting for a slow machine, the diagnostic move is to quit everything in the menu bar, wait a minute, and see whether the machine changes. If it does, add them back in halves until it slows down again.

Browser tabs and extensions. A browser with forty tabs is forty renderer processes. Chrome and Safari both have a per-tab task manager (Chrome: Window → Task Manager; Safari: Develop → Show Web Inspector, or Activity Monitor where the processes are named after the tab’s site). Extensions are the worse offender because they run in every tab: an ad blocker, a password manager, three shopping helpers and a screenshot tool each inject script into every page you open.

Cause 3: the machine is throttling

If CPU is low, memory pressure is green and the disk has room, but the machine still feels slow — especially in bursts, especially when it is warm — you are looking at thermal throttling. Apple Silicon throttles aggressively and quietly: it will hold clock speeds down rather than spin fans up, because the SoC is designed to run at the edge of its thermal envelope and the fan curve is deliberately lazy.

Two ways to confirm it. sudo powermetrics --samplers smc -n 1 prints CPU and GPU die temperatures and the current fan RPM on Apple Silicon and Intel alike. pmset -g therm prints the current thermal pressure level and, if the system is throttling, the reason. A machine sitting at 95°C with the fans at 2000rpm is being held back; the same machine at 60°C is not.

The fixes are physical. Vents blocked by a laptop sleeve, a cushion or a closed cabinet; a fan packed with dust; a battery that has swollen and is pressing on the chassis — all show up as sustained heat with no CPU load to explain it. coconutBattery reads battery health and cycle count from the battery’s own controller, and a health figure in the low 80s or below on a machine that also runs hot is worth a hardware check.

On Intel Macs there is a second cause of the same symptom: a discrete GPU that is being switched on for no reason. gfxCardStatus and similar tools show which GPU is active; a laptop that has been pushed onto the discrete chip by a background app runs hot and drains battery for nothing.

Cause 4: a network volume is stalling Finder

This one produces a symptom that looks nothing like its cause. Finder hangs for thirty seconds when you open a window, save dialogs take forever, apps that use the file picker beachball — and Activity Monitor shows nothing wrong, because the time is spent in a kernel wait on a network round trip.

It happens when Finder has a mounted SMB or NFS share that has gone away: a NAS that slept, a VPN that dropped, a server that was renamed. The mount is still in the mount table, so every file operation tries it and waits for a timeout.

Check with mount or df -h in Terminal. Anything in the list you do not recognise, especially anything with an IP address or a .local name, is a candidate. diskutil unmount force /Volumes/<name> removes a stuck mount without a reboot. Then stop Finder from reopening it: Finder → Settings → General → Connected servers, and remove the share from Login Items.

If you genuinely need the share, mount it on demand rather than at login, and prefer a protocol that fails fast. AFP is deprecated and gone from current macOS; SMB is the only real option for a Mac-to-NAS connection, and setting the share to mount manually is the difference between a machine that waits thirty seconds at startup and one that does not.

Cause 5: Spotlight is reindexing, repeatedly

A single reindex after a migration or an OS upgrade is normal and finishes. A Mac that reindexes every week is broken, and it will feel slow in exactly the way indexing does: bursts of disk activity, mdworker processes in the CPU list, fans coming on for no visible reason.

Check the status with mdutil -s /. If it says Indexing enabled and the machine is quiet, you are fine. If indexing never finishes, the usual causes are a corrupt index, a volume with permission problems, or an exclusion that keeps being re-added.

The repair is to erase and rebuild the index: sudo mdutil -E /. It takes anywhere from ten minutes to several hours depending on how many files you have, and the machine will be slow while it runs. Do it when you are not working.

A subtler variant: an external drive that is indexed, unmounted uncleanly, and remounted causes a partial rebuild every time. If you have a drive you only use for backups, exclude it in System Settings → Spotlight → Search Privacy rather than letting it reindex on every connection.

Cause 6: the Finder itself is the problem

Finder caches window state, icon previews and Quick Look thumbnails, and all three can go bad. The symptoms are specific: icons render as generic documents, Quick Look shows a blank window, a folder takes ten seconds to list files that a terminal ls returns instantly.

Two repairs, in order of disruption. First, relaunch Finder: hold Option and right-click the Finder icon in the Dock, then choose Relaunch. That clears the window state without touching anything on disk. If that does not fix it, delete the icon cache — sudo rm -rf /private/var/folders/*/*/C/com.apple.QuickLook.thumbnailcache — and log out and back in.

If a single folder is slow to open and everything else is fine, look at what is in it. A folder containing a 40,000-file directory, or one with a corrupt extended attribute, will be slow in Finder and fast everywhere else. xattr -l <file> shows the attributes; xattr -c <file> clears them.

Cause 7: the disk is failing

An SSD that is wearing out does not stop working, it slows down. The controller has to retry reads, remap bad blocks, and sometimes the drive falls back to a slower mode. The symptom is a machine that benchmarks normally and then stalls for seconds at a time, with nothing in Activity Monitor to explain it.

Check the drive’s own health report: diskutil info disk0 | grep -i -E "SMART|Solid State". Verified is what you want; anything else is a warning. On Apple Silicon the internal SSD’s health is exposed through system_profiler SPNVMeDataType, which reports the percentage of life used.

This is also the one cause where the fix is not a fix. If the internal SSD is failing, no amount of cleanup helps, and the machine needs service. Back up first — how to back up a Mac to an external drive covers the part people skip.

When reinstalling is the right answer

A clean install fixes exactly one class of problem: accumulated third-party software that you cannot identify. It does not fix hardware, it does not fix a full disk, and it does not make an old machine fast.

If you decide to do it, erase and reinstall rather than installing over the top — the point is to leave the old system’s launch agents behind — and restore your data from a backup rather than a migration, because Migration Assistant will happily copy the same launch agents back. If you use Migration Assistant, plan to spend an hour in /Library/LaunchAgents afterwards.

Before you go that far, try Safe Mode. On Intel, hold Shift at startup; on Apple Silicon, hold the power button until the startup options appear, choose your disk, then hold Shift and click Continue in Safe Mode. Safe Mode loads only Apple’s software and rebuilds a few caches on the way in. If the machine is fast in Safe Mode and slow out of it, the cause is third-party software and a clean install will help. If it is slow in Safe Mode too, it is hardware or the system volume, and a reinstall is a waste of an evening.

What not to do

Do not install a second antivirus on top of the first. Real-time scanners intercept file reads at the kernel level, and two of them intercept each other. The symptom is a machine with low CPU and slow file operations — the time is in the kernel, not in a process.

Do not run a “memory cleaner”. macOS manages memory itself and compressing or purging it on a timer makes the machine slower, because the pages it just evicted have to be read back from disk. The only legitimate memory action is quitting apps you are not using.

Do not disable SIP to install a “speed-up” utility. System Integrity Protection exists to stop exactly this kind of software from modifying the system, and turning it off to gain a few percent is a bad trade. There is a full explanation of what it protects in what System Integrity Protection is.

Do not believe the “your Mac is 3 years old and needs cleaning” pop-up. Those are advertisements, usually from a browser notification you granted by accident, and the number is invented. The same is true of any page that claims to have scanned your machine — a web page cannot read your disk.

A checklist you can run in ten minutes

1. Activity Monitor, CPU tab, sorted by % CPU. Anything above 50% that you did not start: identify it before you kill it.
2. Activity Monitor, Memory tab. Red pressure means close apps; green means stop looking here.
3. System Settings → General → Storage. Free space below 15% of the volume: that is your answer.
4. System Settings → General → Login Items. Remove what you do not recognise from both lists.
5. mount | grep -v "^/dev" in Terminal. Any network mount you did not expect: unmount it.
6. sudo powermetrics --samplers smc -n 1. Above 90°C with nothing running: thermal, not software.
7. Restart. Not because it is a cliché, but because it clears every stuck process and every leaked file handle at once, and it takes ninety seconds.

If all seven come back clean and the machine is still slow, the remaining candidates are the disk and the battery, and both are hardware questions rather than software ones.

FAQ

My Mac is slow only when plugged into a monitor. Why? Connecting a display can push a laptop onto its discrete GPU, and it raises the power budget, which raises heat. On Intel Macs the GPU switch is the usual culprit; on Apple Silicon a 5K or 6K display at high refresh is genuinely more work for the display engine than the internal panel, and the machine runs warmer. If the slowness appears only with the external display attached, look at heat and at the resolution and refresh rate rather than at your apps.

Does adding RAM help? On Intel Macs with replaceable memory, yes, if memory pressure is yellow or red. On Apple Silicon there is no upgrade path — the memory is in the package — so the answer is to close what you are not using, or to buy the next machine with more. Check memory pressure before you assume memory is the problem; a machine with 8GB and green pressure is not short of RAM.

Is it worth upgrading an old Mac instead of replacing it? An SSD upgrade transforms a hard-drive Mac, and on Intel models with a replaceable drive it is the best value per dollar in this entire article. On any Mac from 2018 onwards the storage is soldered or proprietary, so the only upgrade is external. Beyond storage, an old machine is limited by its CPU, and no amount of cleanup changes that.

Why does my Mac slow down when it is on battery? Low Power Mode, which System Settings → Battery turns on automatically below 20%. It reduces display refresh, delays background work and holds the SoC at a lower clock. It is doing what it is designed to do. The other possibility is a battery that can no longer deliver peak current, which the system reports as Service Recommended in the same panel.

Do I need a cleaner app at all? No. Everything in this guide can be done with Finder, Terminal and Disk Utility. A cleaner earns its place when it does the part that is tedious rather than the part that is hard: finding the 40GB of app containers you cannot see, or removing the launch agents an uninstalled app left behind. Judge it on that, not on the number of “junk files” it claims to have found.