Why Is My Computer So Slow? Practical Fixes for Windows and Mac

01Quick answer

A computer running slow is most often doing too much at once: too many apps starting automatically, a drive that is nearly full, updates working in the background, or a laptop that has slowed itself down because it is hot or on battery-saving mode. Restart it, install pending updates, turn off unneeded startup apps and free up storage. All of this uses tools built into Windows and macOS. This guide is for everyday users whose laptop or desktop has become sluggish.

02Before you start

• Back up important files before removing apps or files. Our backup guide shows a simple method.
• Notice when it’s slow. Slow only when starting up points to startup apps. Slow all the time points to storage, background tasks or heat. Slow only in one app points to that app.
• Skip “PC cleaner”, “speed booster” and registry cleaner tools. Windows and macOS already include what you need, and some of these tools are misleading or harmful.
• Be wary of pop-ups saying your computer is infected and asking you to call a number. Close the browser tab; legitimate security tools don’t work that way.

03Why this happens

Usually simple to fix:

• The computer hasn’t been restarted in a long time.
• Many apps launch at startup and keep running in the background.
• The main drive is nearly full, leaving little room for the system to work.
• Updates are downloading or installing in the background.
• Too many browser tabs or extensions are open.
• A laptop is in a battery-saving mode or is running hot and slowing itself down.

Needs the manufacturer or a repair service:

• The drive is failing, which may show as very slow file opening, clicking noises on older drives or disk warnings.
• The computer is too old for the current operating system or apps you use, and more memory or a newer machine may be needed.

04Quick wins

1. Restart the computer. Use Restart rather than closing the lid. This clears memory and finishes pending updates.
2. Install updates. On Windows, open Settings, then Windows Update. On a Mac, open System Settings, then General, then Software Update. Restart when asked.

   Faster now? If yes, restart once a week or so. If not, continue.

3. Close what you aren’t using, including browser tabs. Remove browser extensions you don’t recognise or need from the browser’s settings.
4. Check the power mode. On Windows laptops, open Settings, System, then Power & battery and choose a balanced or best-performance mode when plugged in. On a Mac laptop, check that Low Power Mode isn’t switched on in Battery settings when you need full speed.

05Deeper fixes

On Windows

1. Turn off unneeded startup apps. Open Settings, then Apps, then Startup, or open Task Manager (Ctrl, Shift and Esc) and choose the Startup apps tab. Turn off apps you don’t need straight away, such as chat apps or update helpers. Leave security software on.
2. See what’s using resources. In Task Manager, sort by CPU, Memory and Disk to find heavy apps.
3. Free up space. Use Storage Sense and the cleanup recommendations in Settings, System, Storage. Our guide to freeing up disk space walks through it safely.
4. Uninstall apps you no longer use from Settings, then Apps.
5. Run a scan with Windows Security. Open the Windows Security app and run a quick scan.

On a Mac

1. Review login items in System Settings, General, Login Items, and remove apps you don’t need at startup.
2. Check Activity Monitor (Applications, then Utilities) for apps using a lot of CPU or memory.
3. Free up storage with the recommendations Apple provides in System Settings, General, Storage.

   What you should see: more free space and fewer apps running at login. Restart and compare.

06Common mistakes to avoid

• Installing “optimiser” or registry cleaner tools from ads or pop-ups.
• Turning off security software to make the computer faster.
• Deleting files or folders you don’t recognise from system locations.
• Resetting the computer before trying the simpler fixes and backing up.
• Ignoring heat. A hot laptop slows itself down; our overheating guide explains what to do.

07If it still doesn’t work

If the computer is still very slow after these steps, Windows and macOS include recovery and reinstall options, but these are a last resort and require a backup first. If updates themselves are stuck, see our Windows Update guide. If you hear unusual noises from the drive, see disk warnings, or the computer is many years old, a qualified repair service or the manufacturer can check the hardware and tell you whether more memory, a new drive or a replacement makes sense.

08The short version

Restart, update, close what you don’t need, trim startup apps and free up storage using built-in tools. Avoid cleaner apps. Lasting slowness with disk warnings or on an older machine needs a professional check.

09FAQ

Why is my computer slow right after an update?

After a major update, Windows and macOS often finish background tasks such as indexing files and optimising apps. Leave the computer on and plugged in for a while, then restart. If it stays slow for days, follow the steps above.

Does restarting really make a difference?

Yes. A restart clears memory, stops apps that have built up in the background and completes pending updates. Many people only close the lid, which puts the computer to sleep without a fresh start.

Should I use a PC cleaner app?

It isn’t needed. Windows and macOS include storage cleanup and startup controls, and some cleaner apps are misleading or bundle unwanted software. Stick to the built-in tools.

Will more memory make my computer faster?

It can help if the computer regularly runs out of memory, which Task Manager or Activity Monitor can show. Many laptops have memory that can’t be upgraded, so check with the manufacturer or a repair service first.