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, or a hard drive that is failing. You can fix the first three yourself in under an hour. The fourth requires a professional, but you will see warning signs before it happens.

Start by checking what is actually running. 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 one program is using more than 50% of either, that is your problem. If nothing stands out, move to the next step.

Next, check how much space is left on your hard drive. On Windows, right-click the C: drive in File Explorer and select Properties. On Mac, click the Apple menu, select About This Mac, then Storage. If you have less than 10% free space, your computer will slow down noticeably. You need room for temporary files and for the system to work.

Key Takeaways

  • Most slowdowns come from too many startup programs, a nearly full hard drive, or malware—all fixable without professional help.
  • Task Manager (Windows) or Activity Monitor (Mac) shows you which programs are using the most processing power and memory right now.
  • Keeping at least 10% of your hard drive free prevents Windows and Mac from slowing down as they manage temporary files.
  • Malware and unwanted toolbars often hide in your browser and startup programs, and removing them usually takes 20 to 30 minutes.
  • If your hard drive is making clicking sounds or your computer freezes for 30 seconds at a time, the drive itself may be failing and you need a professional.

Disable programs that run when you start your computer

Every program you allow to start automatically uses memory and processing power before you even open anything. Many programs set themselves to start automatically without asking. On Windows, open Task Manager, click the Startup tab, and look at the Status column. Anything marked Enabled that you do not use every day can be disabled. Right-click it and select Disable.

On Mac, go to System Settings, then General, then Login Items. Remove anything you do not recognize or do not use daily. Be cautious: do not disable anything with "Apple" or "Security" in the name unless you are certain what it does. When in doubt, leave it alone.

After you disable startup programs, restart your computer. You should notice the startup time drop when ready, and your computer should feel more responsive while you work.

Clear out files and uninstall programs you do not use

If your hard drive is more than 80% full, your computer will slow down. Start by deleting files you no longer need. On Windows, use Disk Cleanup: press Windows key + R, type cleanmgr, and press Enter. Select the drive, check the boxes for Temporary Files and Recycle Bin, and click Delete. On Mac, go to System Settings, General, Storage, and click Recommendations to see what can be removed safely.

Next, uninstall programs you do not use. On Windows, go to Settings, Apps, Apps & Features, and look through the list. Click anything you do not recognize or do not use, then Uninstall. On Mac, open Applications in Finder, drag unused programs to Trash, and empty the Trash. Be careful not to delete anything with "Apple" or "System" in the name.

After you free up space, restart your computer. If you went from 90% full to 50% full, the speed improvement will be noticeable.

Remove malware and unwanted browser toolbars

Malware and unwanted software slow your computer by running in the background and sometimes hijacking your browser. Signs include a new toolbar you did not install, your home page changing on its own, or pop-up ads appearing even when you are not browsing. On Windows, use Windows Defender, which is built in. Press Windows key + I to open Settings, go to Privacy & Security, then Virus & Threat Protection, and click Scan Options. Choose Full Scan and let it run—this can take 30 minutes to an hour.

On Mac, malware is less common, but you can use the built-in Malwarebytes scan or Xprotect. Go to System Settings, Privacy & Security, and scroll to Security. If it says your Mac has not been scanned recently, click Scan Now.

Check your browser extensions and toolbars. In Chrome, click the three dots in the top right, go to Extensions, and remove anything you do not recognize. In Firefox, click the menu button, select Add-ons, and remove suspicious extensions. In Safari, go to Safari menu, Preferences, Extensions, and remove anything unfamiliar. Restart your browser after you remove extensions.

Update Windows or macOS and your drivers

Outdated operating systems and drivers can cause slowdowns and security problems. On Windows, press Windows key + I, go to Update & Security, and click Check for Updates. Install any available updates and restart. On Mac, click the Apple menu, System Settings, General, Software Update, and install any updates available.

Drivers are the software that lets Windows and Mac communicate with your hardware—your graphics card, network adapter, and other components. Outdated drivers can cause lag and crashes. On Windows, right-click the Start button, select Device Manager, and look for any devices with a yellow warning triangle. Right-click those devices and select Update Driver. On Mac, drivers usually update automatically with the operating system, so you do not need to do anything.

Check your hard drive health if the computer is still slow

If you have done all the steps above and your computer is still slow, your hard drive may be failing. Listen for clicking, beeping, or grinding sounds coming from inside the computer. If you hear those, stop using the computer and take it to a professional—a failing drive can lose your files. Do not try to fix this yourself.

You can also check your hard drive's health using free software. On Windows, read CrystalDiskInfo (from the official site only), install it, and run it. Look at the Health Status: if it says Good, your drive is fine. If it says Caution or Bad, your drive is failing. On Mac, Disk Utility can show some information. Open Applications, Utilities, Disk Utility, select your drive, and click Info. If you see any errors, take your computer to a professional.

A failing hard drive cannot be sped up—it needs to be replaced. A professional can back up your files and install a new drive, usually for $150 to $400 depending on the drive type and your location.

Consider an upgrade if your computer is very old

If your computer is more than 7 or 8 years old and you have done all the steps above, the hardware itself may straightforward be outdated. Older processors and RAM cannot keep up with modern software. You have two options: add more RAM (memory), or replace the hard drive with a solid-state drive (SSD).

Adding RAM is the cheaper option if your computer allows it. Most laptops have RAM that can be upgraded, but some newer models do not. A professional can tell you in five minutes whether yours can be upgraded and what it would cost—usually $50 to $150 for the part and installation. An SSD replacement costs more, usually $150 to $300, but makes a much bigger difference in speed.

If your computer is very old and both upgrades would cost more than a few hundred dollars, it may be time to replace it. A professional can help you decide whether an upgrade or replacement makes sense for your situation.

Frequently Asked Questions

Why does my computer slow down over time even if I do not install anything new?

Windows and Mac create temporary files, cache files, and log files as you use the computer. These accumulate in hidden folders and eventually take up significant space. Updates to the operating system and security patches also add files. Running Disk Cleanup (Windows) or Storage recommendations (Mac) every few months prevents this buildup.

Is it safe to disable programs in the Startup tab?

Yes, as long as you do not disable anything with "Windows", "Apple", or "Security" in the name. Most programs that set themselves to start automatically are not essential. If you disable something and your computer stops working correctly, you can re-enable it the same way.

What is the difference between RAM and hard drive space?

RAM is temporary memory your computer uses while programs are running—it is very fast but clears when you restart. Hard drive space is permanent storage for your files and programs. A full hard drive slows your computer down. Low RAM makes your computer slow when many programs are open at once.

Do I need antivirus software if Windows Defender is already on my computer?

No. Windows Defender is built into Windows and is sufficient for most users. Third-party antivirus software can actually slow your computer down because it runs constantly in the background. If you want extra protection, use Windows Defender and be careful what you read.

How often should I restart my computer?

Restart at least once a week. Restarting clears RAM, stops programs that may be using resources in the background, and installs updates that require a restart. Many slowdowns disappear after a straightforward restart because temporary files and stuck processes are cleared.