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 they don't. Suddenly 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 running through treacle.
Before you book a Genius Bar appointment or start browsing John Lewis for a new one, try these seven things in order. 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 to do a million background things: caching, swap files, updates, Time Machine snapshots. When it runs out, everything grinds.
How to check: Apple menu → System Settings → General → Storage. If your bar is mostly full (less than 10-15% free), that's your problem.
What to do: 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 is still there, quietly starting every time you turn the Mac on. Over years, that's a lot.
Where to look: System Settings → General → Login Items & Extensions.
You'll find two sections: "Open at Login" and "Allow in the Background". Both lists are worth pruning. If you see anything you don't recognise or don't need running all the time (Spotify Helper, Adobe Updater, Dropbox, Microsoft AutoUpdate, old printer helpers), remove it. You can always put it back.
4Let Spotlight finish indexing
After a big macOS update or a big file import, Spotlight (the search thing) re-indexes your whole drive. While it's doing that, your Mac runs noticeably slower: CPU is high, fans are on, battery drains faster. It can take hours.
How to check: click the magnifying glass in the top-right and start typing. If it says "Indexing" with a progress bar, leave it alone and come back later. Don't put the Mac to sleep; that pauses indexing.
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, the current version is macOS 26 Tahoe), updating can genuinely make the Mac faster. Apple often ships performance improvements for older hardware in new macOS releases.
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 are constantly running, or you're seeing apps crash regularly, it's worth getting it looked at. On older Intel Macs, this often means dried thermal paste on the CPU (similar to the problem on Intel laptops generally). On newer Macs, it's more likely a software-level issue that needs time to hunt down.
Related reading: how to stop your laptop overheating (same principles apply to Intel MacBooks), and my Mac repair service page for the kinds of jobs I take on.
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.