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How to speed up a slow Mac
A Mac rarely slows down for one reason. It slows down because four or five small things stack up: a startup disk with no breathing room, a login-items list you never curated, memory pressure that pushes data into swap, one runaway process burning CPU, and stale system caches. Work through them in order and you will usually get most of the speed back — no reinstall, no new hardware.
Updated 2026-08-02 · Written by the CleanerMac team · macOS 13–15 tested
First, find out what is actually slow
Guessing wastes hours. Open Activity Monitor (Applications → Utilities, or Spotlight with ⌘Space) and spend two minutes there before you change anything. Look at three tabs in this order.
- CPU — sort by the % CPU column. A single process pinned above 90% for minutes at a time is your answer. Common culprits: a browser tab running a heavy script,
mds/mds_stores(Spotlight indexing, which finishes on its own),photoanalysisdafter a big Photos import, andbackupdduring a Time Machine run. - Memory — ignore the "Memory Used" number and look at the Memory Pressure graph at the bottom. Green means you are fine even if RAM looks full. Yellow or red, with a non-zero and climbing Swap Used, means you genuinely need to close something.
- Disk and Energy — sustained heavy writes from one app, or an app permanently listed under significant energy impact, both point at a specific offender rather than at "my Mac is old".
If nothing looks unusual in Activity Monitor, the problem is almost always storage or startup load, which the next two sections cover.
Give the startup disk room to breathe
macOS uses free disk space constantly — for swap, for temporary files, for app caches, for Time Machine local snapshots. When the boot volume gets close to full, swap has nowhere to go and the whole system starts stuttering. Check what you have: Apple menu → System Settings → General → Storage. The bar chart at the top breaks usage down by category, and each row underneath opens a detail sheet where you can delete individual items.
A practical target is to keep at least 10–15% of the volume free, and never less than about 20 GB on a modern install. If the Storage screen shows a huge, unhelpful "System Data" block, that is normal — it is a catch-all, and it is explained in detail in our guide to System Data storage on Mac. If you are already at the warning stage, start with what to do when the startup disk is full and how to find large files on a Mac.
The fastest real wins, in the order they usually pay off: old .dmg and .pkg installers in ~/Downloads; iOS device backups in ~/Library/Application Support/MobileSync/Backup; Xcode build products in ~/Library/Developer/Xcode/DerivedData and old simulator runtimes; Mail attachments cached under ~/Library/Containers/com.apple.mail; and duplicated media, which is covered in find and remove duplicate files on Mac.
Cut what launches at login and what stays open
Every helper that starts with your session competes for CPU and disk exactly when you want the machine responsive. Go to System Settings → General → Login Items & Extensions. The top list is apps you or an installer added — remove anything you do not consciously use. The lower list, "Allow in the Background", is the one people miss: updaters, sync daemons and printer helpers from software you may have uninstalled years ago. Toggling one off is reversible, so switch off anything unfamiliar and see whether you notice its absence over a week.
Legacy launch agents live in ~/Library/LaunchAgents and /Library/LaunchAgents. You can inspect them in Finder (⇧⌘G, paste the path) — each .plist filename usually names its owner. Leave anything with com.apple. in the name alone. Removing leftovers properly is easier with a real uninstaller; see how to completely uninstall apps on Mac.
Two everyday habits matter just as much as login items. The first is browser tabs: each modern tab can hold hundreds of megabytes, and a hundred open tabs is a genuine memory problem, not a rounding error. The second is a very crowded Desktop — Finder has to generate and cache a preview for every item, so a Desktop with hundreds of large files can slow window redraws and login on older machines; moving them into a single folder helps. Also worth checking: System Settings → Accessibility → Display → Reduce motion and Reduce transparency. Neither adds raw performance, but on Intel Macs and older integrated GPUs they make the interface feel noticeably snappier.
Understand memory pressure before you touch RAM
This is the single most misunderstood part of Mac performance. macOS deliberately fills unused RAM with file caches and compressed pages because idle RAM does nothing for you. Free RAM is not the goal. The goal is low memory pressure and little or no swap activity.
So do not chase a big "free memory" number. If pressure is green, you have nothing to fix. If it is yellow or red, quit the applications at the top of the Memory tab, reduce open browser tabs, and restart if uptime is measured in weeks. sudo purge exists and does flush inactive and cached pages, but it is a diagnostic tool, not a tune-up: macOS immediately begins refilling those caches, and for a few minutes afterwards things can feel slower because files must be read from disk again. Our dedicated page on how to free up RAM on a Mac walks through the numbers honestly.
Clear stale caches and reset system state
Caches make apps faster, so clearing them is not a routine speed trick — but stale or corrupted caches do cause real symptoms: apps hanging on launch, Quick Look showing blank previews, fonts rendering wrong, websites failing to resolve. These are the safe, well-established resets.
| Symptom | What to reset | How |
|---|---|---|
| App launches slowly or misbehaves | That app's user cache | Quit the app, then clear its folder inside ~/Library/Caches |
| Sites fail to load, VPN or DNS change not taking effect | DNS resolver cache | sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder |
| Blank or wrong Quick Look previews | Quick Look cache | qlmanage -r cache |
| Garbled fonts, missing glyphs | Font databases | atsutil databases -remove then log out and back in |
| Finder or Dock glitching, icons stuck | Finder / Dock | killall Finder and killall Dock (both relaunch instantly) |
| Spotlight search returns nothing useful | Search index | sudo mdutil -E / — reindexing takes hours and slows the Mac meanwhile |
Never delete the whole of ~/Library/Caches while apps are open, and never touch /System/Library — it is read-only and protected by SIP for good reason. Step-by-step detail lives in how to clear cache on Mac safely and how to flush the DNS cache.
When it is genuinely the hardware
Be honest about limits. A Mac with a spinning hard drive will never feel fast under a current macOS version; an SSD upgrade transforms it where that is still possible. 8 GB of RAM is workable for browsing and office work and painful for video editing or many containers. Intel MacBooks throttle when the fans are clogged with dust or thermal paste has aged, which shows up as high CPU with low actual throughput. And an SSD that is chronically 99% full will slow down at the controller level, independent of macOS.
If you would rather not run six Terminal commands and audit four folders by hand, that whole maintenance routine is what CleanerMac packages into buttons: cache and log cleanup that automatically skips any app that is currently open, a storage X-ray, and a Tune-Up tab that runs the DNS flush, Quick Look reset, font-cache reset and Finder/Dock restart for you. Your own files go to the Trash, so those removals are recoverable — and it all stays on your Mac, with no account and nothing uploaded.
A maintenance rhythm that actually sticks
- Weekly: restart the Mac. Quit browser windows you are not using. Empty the Trash.
- Monthly: check System Settings → General → Storage, clear the Downloads folder, and review Login Items.
- Quarterly: clear app caches, remove apps you no longer open (with their leftovers), and run a duplicate scan.
- Yearly: verify your Time Machine backup actually restores, and check available free space against that 10–15% target.
None of this requires special software. It requires doing it — which is the only real argument for automating it.
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Frequently asked questions
Why is my Mac suddenly slow when nothing changed?
The most common causes are a background indexing job and a full startup disk. After a macOS update or a large Photos import, processes like mds_stores and photoanalysisd can run hard for hours before settling. Check Activity Monitor's CPU tab first, and if one of those is at the top, simply leave the Mac plugged in and idle for a while.
Does restarting my Mac actually help performance?
Yes, more than people expect. A restart clears swap, releases memory that leaky apps never returned, and resets stuck background daemons. If your uptime is measured in weeks, restart before trying anything more complicated.
Should I run purge to speed up my Mac?
Generally no. sudo purge frees inactive and cached memory, but macOS was using that memory productively and will rebuild the caches immediately. It is useful for benchmarking or diagnosing a specific issue, not as routine maintenance. Watch memory pressure and swap instead of the free-memory figure.
How much free disk space does macOS need to run well?
Aim for at least 10 to 15 percent of the volume free, and try never to drop below roughly 20 GB. macOS needs headroom for swap, temporary files and update staging, and performance degrades sharply as you approach full.
Do cleaning apps really make a Mac faster?
They make maintenance faster, which is not the same claim. Removing junk files reclaims disk space, and clearing a corrupted cache can fix a specific slowdown. Any tool promising a large guaranteed speed increase from deleting files alone is overselling.
Is it worth reinstalling macOS to fix slowness?
Rarely as a first step. A clean install fixes deep configuration problems but costs hours and often reintroduces the same apps and login items. Work through storage, login items, memory pressure and a single runaway process first; reinstall only if the machine is unstable rather than merely slow.