How to Speed Up a Slow Computer (Windows and Mac)

Most “speed up your computer” advice is placebo. The fix that actually works is finding what’s eating your CPU, memory, or disk — open Task Manager (Ctrl + Shift + Esc) on Windows or Activity Monitor on Mac — and acting on that specific cause, not running a cleaner. Work through the steps below in order of real-world impact: diagnose first, then free up disk space, cut startup programs, scan for malware, update software, and only then spend money on hardware.

Start by finding the real bottleneck

A computer feels slow for a concrete reason: the CPU is saturated, it’s out of RAM, the disk is thrashing, or it’s overheating and throttling. Measuring takes two minutes and saves you from guessing.

Windows: Task Manager

1. Press Ctrl + Shift + Esc (or right-click the taskbar and choose Task Manager).
2. On the Processes tab, click the CPU column header to sort by usage, then click Memory, then Disk.
3. If one app is always at the top when the machine feels slow, that app is the culprit — close it, update it, or remove it.
4. Open the Performance tab for the overall picture. Memory at 90%+ or disk pinned at 100% explains most freezes.

Mac: Activity Monitor

1. Open Activity Monitor (Applications → Utilities, or press Cmd + Space and type “Activity Monitor”).
2. Use the CPU, Memory, Energy, and Disk tabs, sorting by % CPU or Memory.
3. In the Memory tab, look at Memory Pressure. Green is healthy; yellow or red means you’re genuinely short on RAM.

The fixes, in order of impact

1. Free up disk space

A nearly full drive is the most underrated cause of slowness. With little free space, both Windows and Mac struggle to manage temporary files and virtual memory. Aim to keep 15–20% of the drive free. Our guide to freeing up disk space covers the safe things to delete — start with your Downloads folder, old installers, and the Recycle Bin or Trash.

2. Cut startup programs

Programs that launch at login slow down every boot and keep running afterwards.

• Windows: open Task Manager → Startup apps → right-click an unnecessary item → Disable.
• Mac: open System Settings → General → Login Items, select an item, and click the − button.

3. Scan for malware

Malware and “browser hijackers” run in the background and steal CPU and network. They often explain a slowdown that appears with no obvious process.

• Windows: open Windows Security → Virus & threat protection → Scan options → Full scan.
• Mac: macOS has built-in protection (XProtect), but adware frequently slips past it. Run a free third-party scan with a tool like Malwarebytes, then remove what it finds.

4. Update the OS and drivers

Outdated software can be slow, unstable, or insecure.

• Windows: Settings → Windows Update → Check for updates. For graphics drivers specifically, use the graphics-card maker’s own updater (NVIDIA, AMD, or Intel) or Windows Update’s optional driver updates.
• Mac: System Settings → General → Software Update. Mac drivers ship with the OS, so updating macOS updates them.

5. Tame your browser

A browser with dozens of tabs and extensions is one of the most common hidden causes of slowness — each tab holds memory and each extension can run constantly.

• Close tabs you aren’t using, or use a tab-suspender feature to unload them.
• Remove extensions you don’t recognise or need (in Chrome, go to chrome://extensions; in Safari, Settings → Extensions).
• A bloated cache can also drag a browser down. See how to clear cache for the steps.

6. Upgrade the hardware — the real fix

If the machine is still slow after all of the above, the bottleneck is hardware, and no software tweak will fix it:

• SSD. Replacing a spinning hard drive with a solid-state drive is the single biggest speed upgrade for an older machine. Boot times and app launches drop from minutes to seconds.
• RAM. If you’re genuinely short on memory (red Memory Pressure on Mac, heavy paging on Windows), adding RAM helps — but only if the RAM isn’t soldered and the CPU or disk isn’t the real limit.

Symptom → likely cause → fix

What does NOT work

Skip these, even though they’re everywhere:

• Registry cleaners. Windows doesn’t slow down because of “registry bloat”. Registry cleaners show impressive-sounding numbers while changing nothing, and can break installed software.
• “Optimizer” and “boost” apps. Memory “cleaners” that force RAM to be freed make Windows reload data from disk, which can actually slow the machine down. Many also bundle adware.
• Defragmenting an SSD. Defrag is for spinning hard drives. On an SSD it does nothing useful and adds unnecessary write wear. Modern systems trim SSDs automatically with TRIM (on by default) — never point a third-party defragger at an SSD.
• Disabling the page file or “superfetch” tweaks. Cargo-cult forum tweaks usually make things worse by removing memory management the OS relies on.

When to replace instead of repair

An SSD upgrade is worth it on a machine that’s otherwise healthy. Consider replacing the computer when:

• It’s well over five years old and the CPU is the bottleneck — pegged at 100% during normal use.
• The RAM is soldered and you can’t add more, or you’re already at 8 GB with red memory pressure.
• The combined cost of an SSD and RAM approaches half the price of a new machine.
• Something else is also failing — battery, screen, fan, or hinge — so repairs add up.

If two or more of those apply, put the money toward a new device rather than nursing an old one.

FAQ

Why is my computer suddenly slow?

Usually a single runaway process, a full disk, or a pending restart. Open Task Manager or Activity Monitor first — it tells you in seconds what changed.

Does more RAM speed up a slow computer?

Only if you’re genuinely short on memory (red Memory Pressure on Mac, heavy paging on Windows). If the CPU or disk is the bottleneck, more RAM won’t help.

Are registry cleaners safe?

No. They don’t deliver measurable speed gains and can damage installed software. Skip them.

Will defragmenting speed up my computer?

Only if you still have a spinning hard disk. On an SSD, defragmentation is pointless and causes extra wear — use TRIM instead.

Is a factory reset the best way to speed up a PC?

It can help by removing accumulated software, but back up your files first. And if the bottleneck is a slow hard disk or too little RAM, a reset won’t fix either.