Why is my Mac running slow?

Is your Mac running slow? These are the checks I’d make before calling anyone — including the ones that catch most people out. Work through them in order; some are quick wins, some need a little patience, and one or two might genuinely surprise you.

Whether you have a MacBook Pro, an iMac or a Mac mini, they all slow down eventually — but “slow” always has a reason: a full drive, a crowded startup, hidden background hogs, or hardware that’s ageing. Here are my best first steps for fixing a slow Mac at home.

Nothing slows a Mac more reliably than a startup drive that’s nearly full. macOS needs breathing room for temporary files, updates and memory management — I recommend keeping at least 10% free, plus roughly the equivalent of your RAM, on the main disk. The same applies to external drives.

Spring clean

Clear space by deleting or moving old films, pictures and documents to a backup drive. Tidy the Desktop, hunt down old files you don’t need, and bin them. If you’re not sure where the space has gone, my guide to the best tools for Mac performance shows how to find the big offenders safely.

When your Mac starts, a surprising amount loads itself in the background — and it keeps running the whole time you’re working.

Manage your Startup Items

Give your Mac a clean start. When you don’t manage your Startup Items, it’s like making your Mac run a race with an 80kg backpack — it’s going to take a bit longer to get moving, right?

On macOS Ventura and later: System Settings → General → Login Items & Extensions — review the list and remove anything you don’t need launching every time. On older macOS versions you’ll find the same list under System Preferences → Users & Groups → your username → Login Items. Use the “–” button to remove items; the shorter the list, the better. This won’t uninstall anything — apps still open normally when you want them.

Too many apps running at once, and your Mac starts to struggle with even simple tasks.

Keep an eye on your active apps

We all dart between apps during the day, but often we only spend a few minutes on some tasks and then leave the app running in the background. That eats valuable resources and slows the tasks you are relying on. When you’ve finished with an app you don’t intend to use for a while, shut it down properly and free up your memory.

Check Activity Monitor — including memory pressure

Activity Monitor (Applications → Utilities) is the honest diagnostic. Look at the Memory tab and the Memory Pressure graph at the bottom:

• ● Green — memory is comfortable; RAM isn’t your problem, and upgrading won’t fix whatever’s bothering you.
• ● Yellow — macOS is working hard. Fine occasionally; a warning sign if it’s constant during everyday use.
• ● Red — the Mac is genuinely short of memory and leaning on the drive. Closing apps helps immediately; more memory helps permanently.

While you’re there, check Swap Used — if it keeps climbing into the gigabytes during normal use, the Mac is using the drive as overflow memory. That’s the classic sign RAM is the bottleneck.

You can also sort the process list by Memory or CPU and quit anything that’s clearly yours and clearly misbehaving (the grey “✕” button top-left). Beware though — this bit is for the want-to-be pros: don’t quit things unless you’re sure they’re non-essential. Some background processes are meant to be there.

You’ve done all the above and your Mac is still slow. Now it’s diagnosis time: the two usual suspects are an ageing mechanical drive (on older Macs) or genuinely insufficient memory. Check out my upgrade guide to see what’s possible for your model — and what the honest verdict is on upgrade-versus-replace.

The fixes above apply to any Mac — but the details differ by machine, and I’ve written dedicated guides for each:

• 🖥️ iMac running slow? → iMac Running Slow Fix: What Actually Works — including what to do when slowness follows an update.
• 💻 MacBook running slow? → How to Speed Up a MacBook Without Guesswork — batteries, heat and browser problems in disguise.
• 🧰 Want the toolbox? → Best Tools for Mac Performance That Really Help — Apple’s built-ins reviewed, plus the third-party tools worth knowing (and the scams to avoid).

And if you’d rather have someone else’s eyes on it: that’s my day job. I visit homes and small businesses across Dorset, diagnose the real cause without jargon, and give you the honest verdict — tidy-up, upgrade, repair, or (rarely) time to replace. Get in touch here.