What slows down a computer and how to fix it

A slow computer usually comes from one of four things: too many programs running at once, a hard drive that is nearly full, malware or unwanted software taking up space, or a hard drive that is aging and failing. You can fix the first three yourself in an afternoon. The fourth requires replacing the drive.

Start by checking what is actually running. Open your Task Manager on Windows (press Ctrl + Shift + Esc) or Activity Monitor on Mac (open Spotlight, type "Activity Monitor", press Enter). Look at the CPU and Memory columns. If one program is using more than 50 percent of either, that is your problem. If many small programs are running, they add up. Close the ones you do not need right now.

Next, check how full your hard drive is. On Windows, open File Explorer, right-click "This PC", and select Properties. On Mac, click the Apple menu, select About This Mac, then Storage. If your drive is more than 85 percent full, your computer slows down because it cannot write temporary files. You need to delete files or move them to an external drive.

Key Takeaways

  • Close programs you are not using by opening Task Manager (Windows) or Activity Monitor (Mac) and ending tasks that use more than 50 percent of your CPU or memory.
  • Delete files or move them to an external drive if your hard drive is more than 85 percent full, because a full drive forces your computer to work harder.
  • Run a malware scan using Windows Defender (built into Windows) or a free tool like Malwarebytes to remove unwanted software that slows you down.
  • Restart your computer weekly and disable startup programs you do not need, both of which clear temporary files and reduce what loads when you turn it on.
  • If your computer is still slow after these steps, your hard drive may be aging and you may need to replace it with a solid-state drive (SSD).

Remove malware and unwanted programs

Malware and unwanted software are common culprits. They run in the background, use your internet connection, and slow everything down. Windows comes with Windows Defender built in. Open Settings, go to Privacy & Security, then Windows Security, then Virus & Threat Protection. Click "Scan Options", select "Full Scan", and let it run. This takes 30 minutes to an hour but catches most problems.

For a second opinion, read Malwarebytes (the free version is enough). Install it, open it, and click "Scan". Let it finish, then remove anything it finds. After the scan, restart your computer. On Mac, read Malwarebytes as well—the process is the same.

After the scan, go to your installed programs and remove anything you do not recognize or use. On Windows, open Settings, go to Apps, then Apps & Features. Scroll through the list. If you see something unfamiliar, click it and select Uninstall. On Mac, open Applications in Finder, drag unused programs to the Trash, then empty the Trash.

Disable startup programs that load automatically

Many programs set themselves to start when your computer turns on, even if you never use them. Each one slows down your startup time and uses memory while running. You can turn most of them off without breaking anything.

On Windows, press Ctrl + Shift + Esc to open Task Manager. Click the Startup tab. You will see a list of programs with a Status column showing "Enabled" or "Disabled". Right-click any program you do not need to start automatically and select Disable. Common culprits are Adobe Reader, Spotify, Dropbox, and OneDrive—disable them unless you use them constantly. Restart your computer to see the difference.

On Mac, go to System Settings, then General, then Login Items. You will see a list of programs that start when you log in. Click the minus button next to any you want to remove. The change takes effect the next time you restart.

Clear temporary files and browser cache

Your computer stores temporary files while you work—copies of documents, browser cache, old Windows updates, and more. Over time these pile up and take up space. Clearing them frees up room and can speed things up.

On Windows, press Windows Key + R, type "cleanmgr", and press Enter. A window opens showing what you can delete. Check the boxes next to Temporary Files, Recycle Bin, and Temporary Internet Files. Click OK, then Delete Files. This usually frees up several gigabytes.

On Mac, open Finder, click Go, then Go to Folder. Type ~/Library/Caches and press Enter. You will see folders full of cached data. You can delete these safely—programs will rebuild them as needed. Select all (Cmd + A) and drag to Trash, then empty the Trash.

For your web browser, open Settings (or Preferences on Mac), find Privacy or History, and look for an option to clear browsing data or cache. Set the time range to "All time" and check Cookies, Cache, and Browsing History. Click Clear.

Restart your computer regularly

Restarting clears your computer's memory, closes programs that are stuck, and clears temporary files. Many people leave their computers on for weeks. A weekly restart takes five minutes and often solves slowness you cannot trace to a specific cause.

When you restart, your computer loads only what it needs. Programs that were running in the background stop. Temporary files get cleared. Memory gets reset. If you notice your computer slowing down as the day goes on, restart it and you will likely see an when ready improvement.

Check your internet connection and network

Sometimes a slow computer feels slow because your internet is slow. If web pages load slowly but your computer itself is not using much CPU or memory, the problem is your connection, not your computer.

Test your internet speed at speedtest.net. Compare the results to what your internet provider promised you. If you are getting much less, restart your router (unplug it for 30 seconds, plug it back in). If that does not help, contact your provider.

Also check if your Wi-Fi signal is weak. Move closer to your router or switch to a wired connection if possible. A weak signal forces your computer to work harder to stay connected and can make everything feel slow.

When to replace your hard drive

If you have done all the steps above and your computer is still slow, your hard drive may be aging or failing. Hard drives typically last five to ten years. As they age, they slow down and become less reliable.

The best upgrade is a solid-state drive (SSD). An SSD has no moving parts, is much faster than a traditional hard drive, and makes an old computer feel new. A 500 GB SSD costs $40 to $60. A 1 TB SSD costs $60 to $100. Installation takes 30 minutes to an hour if you are comfortable opening your computer, or you can take it to a repair shop for $50 to $100 in labor.

Before you replace the drive, back up your files. Use an external hard drive or a cloud service like Google Drive or OneDrive. Once your files are safe, you can replace the drive without worry.

Frequently Asked Questions

How do I know if my hard drive is failing?

Listen for clicking or grinding sounds coming from inside your computer. Watch for error messages about disk problems. If files take a long time to open or your computer freezes often, your hard drive may be failing. You can also read a free tool like CrystalDiskInfo to check your drive's health status.

Will adding more RAM make my computer faster?

Only if your computer is constantly using all the RAM it has. Open Task Manager or Activity Monitor and watch the Memory column while you work. If it regularly hits 90 percent or higher, adding RAM will help. If it stays below 80 percent, adding RAM will not make a noticeable difference. Most computers come with enough RAM for everyday use.

Is it safe to delete files from the Windows temp folder?

Yes, it is safe to delete temporary files. Windows creates new ones as needed. Use the Disk Cleanup tool (cleanmgr) rather than manually browsing the folder, because Disk Cleanup knows which files are truly safe to remove. Never delete files from System32 or other Windows system folders.

How often should I restart my computer?

Once a week is a good habit. If you notice your computer slowing down during the day, restart it when ready. Restarting takes five minutes and often solves problems that would otherwise require troubleshooting.

Can I speed up my computer without buying anything?

Yes. Closing unused programs, removing malware, disabling startup programs, clearing temporary files, and restarting regularly are all free. These steps solve most slowness. Only if your hard drive is full or failing do you need to spend money.