Why Is My Computer So Slow? 15 Fixes for Windows 11 and Mac

Why is my computer so slow? In most cases it is one of five things: too many apps starting with the computer, a nearly full drive, too little memory for what you have open, pending updates, or unwanted software running in the background. Old hardware, especially a spinning hard drive, is the next suspect. This guide shows you how to find which one it is in two minutes, then walks through 15 fixes for Windows 11 and Mac, starting with the free and fast ones.

Quick answer: Restart the computer, then open Task Manager (Ctrl + Shift + Esc) on Windows or Activity Monitor on a Mac to see what is using the CPU, memory and disk. Turn off startup apps you don’t need, free up at least 10-15% of your drive, install updates and run a malware scan. If it is still slow with only a browser open, the computer probably needs more RAM or an SSD.

First, find out what is slowing your computer down

Guessing wastes time. Both Windows and macOS have a built-in tool that shows exactly what is using your computer’s resources.

On Windows 11: Task Manager

1. Press Ctrl + Shift + Esc to open Task Manager.
2. On the Processes page, click the CPU, Memory or Disk column header to sort by the biggest user.
3. Open the Performance page to see overall use. If Memory sits above about 90% or Disk sits at 100% for minutes at a time, you have found your bottleneck.
4. Check the Startup apps page to see how many programs launch when Windows starts.

On a Mac: Activity Monitor

1. Open Finder, go to Applications > Utilities and open Activity Monitor (or press Command + Space and type its name).
2. Click the CPU tab and sort by % CPU to find apps working hard.
3. Click the Memory tab and look at the Memory Pressure graph at the bottom. Green is fine; yellow or red means your Mac is short of memory for what you have open.
4. The Disk tab shows which apps are reading and writing the most.

What the results mean

15 fixes to speed up your computer

Work through these in order. The first eight are free, take a few minutes and solve most problems.

1. Restart properly

A restart clears memory, ends stuck background processes and finishes installing updates. On Windows, choose Start > Power > Restart (a restart is more thorough than Shut down, which can use Fast Startup). On a Mac, choose Apple menu > Restart. If you only ever close the lid, your computer may not have restarted in weeks.

2. Close apps and browser tabs you aren’t using

Every open app and tab uses memory. Browsers are often the biggest user on the whole system, and some extensions run all the time in the background. Close tabs you don’t need, quit apps rather than just minimising them (on a Mac, Command + Q), and remove browser extensions you don’t recognise or no longer use.

3. Turn off startup apps (Windows)

Many programs add themselves to startup when you install them. Open Task Manager, go to Startup apps, right-click anything you don’t need right after switching on (chat apps, game launchers, updaters) and choose Disable. The Startup impact column shows which ones matter most. Don’t disable your antivirus or drivers for touchpads and audio.

4. Remove login items (Mac)

Go to Apple menu > System Settings > General > Login Items (called Login Items & Extensions in newer versions of macOS). Select apps under Open at Login that you don’t need and click the minus button. You can also switch off apps listed under Allow in the Background, but only if you know what they do.

5. Install system and app updates

Updates fix bugs that cause slowdowns and often improve performance. On Windows, go to Settings > Windows Update > Check for updates, and look under Advanced options > Optional updates for driver updates. On a Mac, go to System Settings > General > Software Update. Update your browser and other heavy apps too. Note that a large update downloading in the background can itself make the computer slow for a while, so let it finish.

6. Free up disk space

A nearly full drive slows everything down, because the system needs free space for temporary files and memory swapping. Aim to keep at least 10-15% free.

• Windows 11: go to Settings > System > Storage. Open Temporary files to remove them, and turn on Storage Sense to clean up automatically. Empty the Recycle Bin and move big videos and photos to an external drive or cloud storage.
• Mac: go to Apple menu > System Settings > General > Storage and follow the recommendations, such as storing files in iCloud and emptying the Trash automatically. Our guide on clearing cache on a Mac shows how to do it safely.

7. Uninstall apps you no longer use

Unused apps take up space and some run background services. On Windows, go to Settings > Apps > Installed apps, click the three dots next to an app and choose Uninstall. Remove trial software that came with the PC as well. On a Mac, drag unwanted apps from the Applications folder to the Trash (use the app’s own uninstaller if it has one).

8. Scan for malware and unwanted software

Malware, adware and crypto-mining programs can quietly use your CPU around the clock. On Windows 11, go to Settings > Privacy & security > Windows Security > Virus & threat protection and run a Quick scan; run a full scan if you are suspicious. On a Mac, keep macOS updated, remove any app you don’t remember installing, and only install software from the App Store or developers you trust. You don’t need to buy a “cleaner” app to do any of this.

9. Stop apps running in the background (Windows)

Some apps keep working after you close them. In Settings > Apps > Installed apps, click the three dots next to an app, choose Advanced options and set Background app permissions to Never, where that option is offered. While you are in Settings, turn off notifications you don’t need in Settings > System > Notifications.

10. Turn down visual effects (Windows)

Animations, shadows and transparency look nice but use resources on older or low-end PCs. Search the Start menu for Adjust the appearance and performance of Windows, open the Visual Effects tab and pick Adjust for best performance. You can turn smooth fonts back on afterwards if text looks rough.

11. Check your power mode

Battery-saving settings slow the processor down on purpose. On Windows 11, go to Settings > System > Power & battery > Power mode and choose Best performance when the laptop is plugged in (it uses more power). On a MacBook, check that Low Power Mode is off in System Settings > Battery when you need full speed.

12. Optimize your drives (Windows)

Search Start for Defragment and Optimize Drives, select your drive and click Optimize. Windows defragments hard drives and sends a maintenance command (TRIM) to SSDs, and it normally does this on a schedule, so check that the schedule is on. On a Mac, if you suspect disk problems, open Disk Utility and run First Aid on your startup disk.

13. Check for overheating and dust

When a computer gets too hot, the processor slows itself down to protect itself. If the fans are loud and the case feels hot, make sure the vents aren’t blocked (laptops on beds and sofas are a classic cause) and clean dust from the vents with short bursts of compressed air while the computer is off. On a desktop PC, check that all fans spin.

14. Add more RAM or switch to an SSD

If your computer is still slow with only a browser and one or two apps open, the hardware is the limit. Two upgrades make the biggest difference:

• Swap a hard drive for an SSD. If Task Manager’s Performance page lists your drive as HDD, moving to an SSD is the single biggest speed-up for an older PC: faster start-up, apps that open in seconds and no more 100% disk.
• Add RAM. For everyday use with many browser tabs, 8 GB is the practical minimum and 16 GB is comfortable. Check whether your model has a free or replaceable memory slot first; many thin laptops have memory soldered to the board.

Macs with Apple silicon (M-series chips) and most recent Macs can’t be upgraded after purchase, so free up memory and storage instead, or plan for more RAM when you next buy. For desktops, our guide to keeping your PC running smoothly covers regular maintenance too.

15. Reset or reinstall as a last resort

If years of installs and leftovers have built up, a fresh start can make an old computer feel new. Back up your files first.

• Windows 11: go to Settings > System > Recovery > Reset this PC. You can keep your personal files or remove everything. Our step-by-step guide to factory resetting Windows 11 explains each option.
• Mac: recent Macs can erase all content and settings from System Settings, after which you set the Mac up again and restore your files from a Time Machine backup or iCloud. Follow Apple’s own instructions for your model on Apple Support (external site).

Which fix should you try first?

• Slow when you switch it on: fixes 1, 3 and 4.
• Slow with lots of tabs open: fixes 2 and 14 (more RAM).
• Got slow suddenly: fixes 5 and 8. A sudden slowdown often follows an update in progress or new unwanted software.
• Slowly got worse over years: fixes 6, 7, 14 and, if needed, 15.
• Laptop slow on battery only: fix 11.

For more Windows tweaks, see our list of ways to make your computer run faster.

Frequently asked questions

Why is my computer so slow all of a sudden?

A sudden slowdown usually has a single cause: an update installing in the background, a new app or browser extension, malware, or a drive that has just filled up. Open Task Manager or Activity Monitor to see what is using the most CPU, memory or disk, and deal with that first.

How do I speed up my computer for free?

Restart it, disable startup apps, close unused tabs and apps, free up disk space, uninstall software you don’t use, install updates and run the built-in malware scan. Together these fix most slow computers without spending anything.

Do PC cleaner apps make a computer faster?

Windows and macOS already include the tools you need to remove temporary files and manage startup apps. Paid cleaners rarely add much, and some bundle unwanted software of their own. Use the built-in tools first.

How much RAM do I need so my computer isn’t slow?

For web browsing, email and office apps, 8 GB is the minimum that feels smooth today, and 16 GB is better if you keep many tabs open or edit photos. Video editing and gaming need more.

Will resetting Windows 11 make my PC faster?

Often, yes, if the slowdown comes from years of leftover software and settings. It won’t help if the hardware itself is the limit, such as an old hard drive or too little RAM. Try the other fixes first and back up before you reset.