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 almost full, malware or viruses, or a hard drive that is aging and failing. You can fix the first three yourself in an hour or two. The fourth requires replacing the drive, which a repair shop can do.
Start by checking which of these is your problem. Open your Task Manager (press Ctrl+Shift+Esc on Windows, or Command+Space then type Activity Monitor on Mac). Look at the CPU and Memory columns. If they are both under 50% and your disk is not full, your slowness may be from a failing drive — that one needs professional help. If either is above 70%, or if your C: drive shows less than 10% free space, you have a fixable problem.
Key Takeaways
- Close programs you are not using, especially web browsers with many tabs open, because they use RAM and slow everything else down.
- Delete files you no longer need and empty your Recycle Bin or Trash, because a hard drive that is more than 90% full runs slowly even if you are not using it.
- Restart your computer weekly, because it clears temporary files and stops programs from piling up in memory.
- Disable startup programs that run automatically when you turn on your computer, because they load into memory even if you never use them.
- Run a malware scan with Windows Defender or Malwarebytes if your computer is slow even when nothing is open, because viruses and spyware consume CPU and bandwidth.
Close programs and browser tabs you are not using
Open programs sit in your computer's RAM (memory), and when RAM fills up, your computer slows down dramatically. The biggest culprit is usually your web browser. A single browser window with 20 tabs open can use 2 to 4 gigabytes of RAM. Close tabs you are not actively reading, and close the browser entirely when you are done.
Check Task Manager (Ctrl+Shift+Esc) and look at the Memory column. Click the Memory header to sort by highest use. Close any program you recognize and are not using right now. Microsoft Edge, Google Chrome, and Firefox are the usual suspects. Closing them frees up RAM when ready, and your computer should respond faster within seconds.
If you find yourself with many tabs open regularly, consider using a tab manager extension like The Great Suspender or OneTab. These pause tabs you have not looked at in a while, freeing their memory until you click back to them.
Delete files and empty your Recycle Bin
A hard drive that is more than 90% full runs slowly because the drive has no room to write temporary files. Check how much space you have left: right-click your C: drive (or your main drive on Mac), select Properties, and look at the pie chart. If the blue section takes up more than 90% of the circle, you need to delete files.
Start by emptying your Recycle Bin (Windows) or Trash (Mac). Right-click the icon on your desktop and select Empty Recycle Bin or Empty Trash. This frees up space when ready. Next, delete files you no longer need: old downloads, duplicate photos, videos you have already watched, or programs you no longer use. Move large files like old backups or video projects to an external drive if you want to keep them.
If you are not sure what is taking up space, read WinDirStat (Windows) or Disk Diag (Mac). These tools show you exactly which folders are largest, so you can delete the ones you do not need. Aim to get your drive below 80% full.
Restart your computer weekly
Restarting clears temporary files and stops programs from accumulating in memory. Even if you close a program, some of its processes can stay running in the background. A restart wipes the slate clean. You should restart at least once a week, or more often if you leave your computer on 24/7.
When you restart, your computer loads only the programs it needs to run, not every program you have ever opened. This is why a computer often feels faster right after a restart, even if nothing else has changed. Set a reminder to restart every Sunday evening, or enable automatic restarts in your settings.
Turn off startup programs
Many programs are set to launch automatically when you turn on your computer, even if you never use them. These programs load into memory and run in the background, slowing everything down. You can disable most of them.
On Windows, press Ctrl+Shift+Esc to open Task Manager, then 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 (avoid Windows Defender, your antivirus, and any program made by Microsoft or your computer manufacturer) and select Disable. Restart your computer for the change to take effect.
On Mac, go to System Preferences, then General, then Login Items. Select any program you do not need and click the minus button to remove it. The next time you restart, those programs will not load.
Run a malware and virus scan
If your computer is slow even when nothing is open, malware or a virus may be running in the background and consuming CPU power or bandwidth. Windows comes with Windows Defender, which is built in and runs automatically. You can also run a manual scan to check for infections.
On Windows, click the Start button, type Windows Defender, and open Windows Security. Click Virus and threat protection, then Manage settings. Scroll down and click Run a scan under Current threats. Select Full scan and click Scan now. This takes 30 minutes to an hour, but it checks every file on your computer.
If you want a second opinion, read Malwarebytes (the free version is fine). Install it, open it, and click Scan. This catches some threats that Windows Defender misses. If either scan finds something, follow the prompts to remove it, then restart your computer.
Upgrade your RAM or replace your hard drive
If you have done all of the above and your computer is still slow, the hardware itself may be the problem. RAM is inexpensive and straightforward to upgrade. If Task Manager shows Memory at 90% or higher even when you have closed everything, adding more RAM will help. A technician can install it in 15 minutes, or you can do it yourself if you are comfortable opening your computer.
If your hard drive is more than five years old and you have freed up space but the computer is still slow, the drive may be failing. Failing drives slow down because they take longer to read and write files. A repair shop can replace it with a solid-state drive (SSD), which is much faster than an old mechanical drive. This is the most expensive fix, but it usually makes the biggest difference.
Frequently Asked Questions
Why is my computer slow even when nothing is open?
Background processes, malware, or a failing hard drive are usually the cause. Open Task Manager and check the CPU and Memory columns. If either is above 50%, a background process is running. If both are low but the disk is full or the drive is old, the problem is hardware.
Will disabling startup programs break anything?
No, as long as you avoid programs made by Microsoft or your computer manufacturer. Disabling a startup program just stops it from launching automatically — you can still open it manually whenever you need it. If something stops working, you can re-enable it in the Startup tab.
How much free space should I have on my hard drive?
At least 10% to 15% of your total drive space should be free. If your drive is 500 gigabytes, keep at least 50 to 75 gigabytes empty. This gives your computer room to write temporary files and keeps the drive from slowing down.
Is it safe to delete files from my Downloads folder?
Yes, if you have already installed or used them. Installers and old downloads take up space and are safe to delete once the program is installed. Keep only files you actively use or need to reference later.
What is the difference between RAM and hard drive space?
RAM is temporary memory your computer uses while programs are running. Hard drive space is permanent storage for files and programs. A full hard drive slows down your computer. Too little RAM makes it slow when you have many programs open. You need both to be healthy.