Why Is Your Mac Running Slow? 7 Things to Try First
Macs have a reputation for "just working". And to be fair, they largely do. Until one day yours doesn't. The spinning beachball shows up every time you open Mail, Safari takes ten seconds to load a tab, and your three-year-old MacBook feels like it's wading through treacle.
Try these seven things in order before you book a Genius Bar appointment or browse John Lewis for a replacement. Most of the "my Mac is broken" calls I get turn out to be one of the first three.
1Check your storage
This is the single most common cause of a slow Mac I see. macOS needs free space for caching, swap files, updates, Time Machine snapshots. When it runs out, everything grinds.
Apple menu → System Settings → General → Storage. If your bar is mostly full (less than 10-15% free), that's your problem.
The same Storage screen has a "Recommendations" panel. Review large files, empty your Downloads folder, delete old iMovie and GarageBand libraries (they're huge), and empty Trash in Mail and Messages. On my own Mac the biggest culprits are always Photos and Downloads.
2Restart it. Really restart it.
"Mac users never shut down" is a real thing. Closing the lid puts it to sleep. It doesn't restart. After weeks of sleeping and waking, little bits of memory don't get freed, apps leak, and everything slows. A proper restart clears all of it in 30 seconds.
Apple menu → Restart. Untick "Reopen windows when logging back in". Let it come back clean.
3Prune your login items
Every app you've ever installed that asked "can I open at login?" and you clicked yes? Still there. Quietly starting every time you turn the Mac on. Over years, that adds up.
System Settings → General → Login Items & Extensions. You'll find two sections: "Open at Login" and "Allow in the Background". Both are worth pruning. Spotify Helper, Adobe Updater, Dropbox, Microsoft AutoUpdate, old printer helpers. If you don't recognise it or don't need it running all the time, remove it. You can always put it back.
4Let Spotlight finish indexing
After a big macOS update or a big file import, Spotlight re-indexes your whole drive. While it's doing that, everything runs noticeably slower. CPU pegged, fans on, battery draining. Can take hours.
Click the magnifying glass in the top-right and start typing. If it says "Indexing" with a progress bar, that's your answer. Leave it alone and come back later. Don't put the Mac to sleep or it pauses indexing and takes even longer.
5Close your browser tabs
Safari and Chrome are the heaviest things most people run on a Mac. Forty open tabs, several of them running video, one left on Gmail, another on Docs, another on a BBC News article from three days ago, all eating RAM.
On a MacBook Air with 8GB of RAM, heavy browser use alone will make the whole machine crawl. If the slowness correlates with your browser being open, that's your smoking gun.
Also worth a look: extensions. Especially ad blockers, price-comparison tools, and anything that says it "enhances" pages. They do, but at a cost.
6Check your macOS version
Apple menu → About This Mac. If you're more than one major version behind (as of May 2026, current is macOS 26 Tahoe), updating can genuinely make the Mac faster. Apple ships performance improvements for older hardware more often than people realise.
One caveat: only update if your Mac is officially supported for the newer version. Installing an unsupported OS via third-party tools is a great way to turn a slow Mac into a broken Mac.
Also make sure you've installed the latest point release of whatever version you're on; they usually contain bug fixes that help performance.
7Consider the hardware
If none of the above helps, you may be running into a hardware limit:
- Older Intel Macs (pre-2020) with spinning hard drives or 4GB of RAM are at the end of what they can realistically do in 2026. An SSD upgrade on a 2015-era iMac is a game-changer and often cheaper than a new Mac. RAM upgrades vary by model; some are soldered, some aren't.
- MacBook Airs with 8GB RAM struggle with heavy multitasking. You can't upgrade the RAM later (it's soldered on Apple Silicon Macs), so the only fix is a newer model with more RAM.
- Full SSDs on Apple Silicon Macs slow down noticeably as they approach full. Internal SSDs on these machines aren't user-upgradeable either, so if yours is full, you're looking at external storage or a replacement.
Other Quick Wins
- Turn off motion effects: System Settings → Accessibility → Display → Reduce Motion. Tiny win on older Macs.
- Check Activity Monitor: Finder → Applications → Utilities → Activity Monitor. Sort by CPU and RAM, and you'll often spot one runaway app using 100% of something.
- First Aid the drive: Disk Utility → First Aid on your startup disk. Fixes minor file system issues.
When to Bring It In
If you've been through all seven and it's still dragging, or if the Mac is very hot, fans constantly running, apps crashing regularly, it's worth getting it looked at. On older Intel Macs this often means dried thermal paste on the CPU. Same problem Intel laptops get. On newer Macs, it's more likely a software-level issue that needs time to hunt down.
I wrote about laptop overheating fixes if your Intel MacBook runs hot (same principles apply). And if you'd rather just hand it over, I do Mac repairs in St Helens.
Mark has been fixing computers since the late '90s and went self-employed in 2008. Based in St Helens since 2013, he works evenings and weekends from his home in Laffak — friendly, affordable repairs for PCs, laptops, and Macs. See reviews on Google
Still slow after all that?
Bring your Mac in — or I'll come to you — and I'll work out exactly what's slowing it down. No "Genius Bar" appointment needed.
★★★★★"Fantastic service, fixed my MacBook and managed to save all the work for us. One phonecall and we were able to drop the MacBook off straight away and all sorted within 24 hours — over the bank holiday weekend. Would highly recommend"
— Mary-Anne Johnson, via Google