What's Actually Slowing Your Computer Down

A slow computer usually comes from one of three things: too many programs running at once, a hard drive that's nearly full, or malware and temporary files piling up. The good news is that you can check and fix each one yourself in under an hour, and most fixes cost nothing.

Before you start, restart your computer. This clears out temporary memory and stops programs that got stuck running in the background. If the slowness stops after a restart, you're done. If it comes back within a few hours, one of the fixes below will solve it permanently.

Key Takeaways

  • Restart your computer first—it clears temporary memory and often solves slowness on its own.
  • Check how much hard drive space is free by opening File Explorer (Windows) or Finder (Mac) and looking at your main drive; if it shows less than 20 percent free, delete old files or programs you don't use.
  • Open Task Manager (Windows) or Activity Monitor (Mac) to see which programs are using the most memory and CPU, then close the ones you're not actively using.
  • Disable startup programs that launch automatically when you turn on your computer, since each one slows down boot time and uses memory all day.
  • Run a malware scan using Windows Defender (built into Windows) or a free tool like Malwarebytes to catch unwanted software that slows performance.

Check How Much Hard Drive Space You Have Left

Your computer needs free space on the hard drive to run smoothly. When the drive is more than 80 percent full, everything slows down because the system can't write temporary files. On Windows, right-click your C: drive in File Explorer and select Properties. On Mac, click the Apple menu, choose About This Mac, then click Storage. Look at the bar that shows how much space is used and how much is free.

If you have less than 20 percent free space, delete files you don't need. Start with your Downloads folder—most people have old installers and documents there they forgot about. Then check your Documents and Pictures folders for duplicates or old backups. If you're still low on space, uninstall programs you haven't used in months. On Windows, go to Settings > Apps > Apps & Features, find the program, and click Uninstall. On Mac, open Applications, drag unused programs to the Trash, and empty it.

Close Programs That Run in the Background

Every program running uses memory and processing power, even if you can't see it. On Windows, press Ctrl+Shift+Esc to open Task Manager. On Mac, press Command+Space, type Activity Monitor, and press Enter. Look at the CPU and Memory columns—the programs at the top are using the most resources.

Close anything you're not actively using. On Windows, click the program name and click End Task. On Mac, click the program name and click the X button at the top left. Don't close anything labeled System or Windows processes—those keep your computer running. If you're not sure what a program is, search its name online before closing it. After you close a few programs, your computer should feel noticeably faster.

Turn Off Programs That Start Automatically

Many programs are set to launch when you turn on your computer, which slows down startup and uses memory all day. On Windows, open Task Manager (Ctrl+Shift+Esc), click the Startup tab, and look at the list. Right-click any program you don't need to start automatically and select Disable. Common culprits are Adobe Reader, Spotify, Discord, and cloud storage programs—you can always launch them manually when you need them.

On Mac, go to System Settings > General > Login Items. Look at the list under Allow in the Login Items section and click the minus button next to anything you don't want to start automatically. Disabling startup programs won't delete them—they'll still be on your computer, just not running in the background. This change takes effect the next time you restart.

Delete Temporary Files and Browser Cache

Windows stores temporary files that pile up over time and take up space. On Windows 10 or 11, go to Settings > System > Storage > Temporary Files and click Delete. On Mac, you can use the built-in Storage Management tool: go to System Settings > General > Storage, click Recommendations, and follow the prompts to delete old files and empty the trash.

Your web browser also stores cached files—copies of websites you've visited—to load them faster next time. Over months, this cache grows large and can slow things down. In Chrome, press Ctrl+Shift+Delete (Windows) or Command+Shift+Delete (Mac), select All Time, check Cookies and Other Site Data and Cached Images and Files, and click Delete. In Firefox and Edge, the process is similar: look for Clear Recent History or Clear Browsing Data in the menu.

Run a Malware Scan

Malware and unwanted software can slow your computer significantly. Windows comes with Windows Defender built in. Open Settings, go to Privacy & Security > Virus & Threat Protection, and click Scan Options. Select Full Scan and click Scan Now. This takes 15 to 30 minutes but runs in the background while you work.

If you want a second opinion, read Malwarebytes (the free version is sufficient). Install it, open the program, and click Scan. Let it finish completely—don't interrupt it. If it finds anything, click Quarantine to remove it. After the scan finishes, restart your computer. Malware often hides in startup programs and background processes, so removing it can make a dramatic difference in speed.

Upgrade Your RAM or Switch to a Solid State Drive

If your computer is still slow after trying the steps above, the hardware itself may be the limit. RAM (memory) is what your computer uses to run programs. If you have less than 8 GB, upgrading to 16 GB can make a noticeable difference, especially if you use many programs at once or work with large files. Check how much RAM you have: on Windows, right-click This PC and select Properties; on Mac, click the Apple menu and select About This Mac. Look for the Memory line.

A solid state drive (SSD) is faster than an older hard drive (HDD). If your computer is more than five years old and still has a traditional hard drive, replacing it with an SSD will make the biggest speed improvement you can get. This is a more involved upgrade—you may want to take it to a repair shop—but it transforms how fast your computer boots and opens programs. New computers almost always come with SSDs, so this mainly applies to older machines.

Frequently Asked Questions

How often should I restart my computer?

Restart at least once a week, or whenever you notice slowness. Restarting clears memory and stops programs that get stuck. If your computer slows down every few hours, restart daily until you identify and fix the underlying cause using the steps above.

Is it safe to disable startup programs?

Yes, as long as you don't disable Windows system processes. Programs like Spotify, Discord, Adobe Reader, and cloud storage can be safely disabled—you'll just launch them manually when needed. If you're unsure about a program, search its name online or leave it enabled.

Will deleting temporary files remove my documents or photos?

No. Temporary files are system files your computer creates and discards automatically. Deleting them won't affect your documents, photos, or any files you created. Browser cache is also safe to delete—websites will straightforward reload slightly slower the first time you visit them after clearing it.

What's the difference between a virus and malware?

A virus spreads by copying itself to other files, while malware is any unwanted software that harms your computer. Malware includes spyware, adware, and ransomware. Windows Defender and Malwarebytes catch both, so the distinction doesn't matter for removing them.

Can I speed up my computer without buying anything?

Yes. All the steps in this guide are free. Restarting, closing background programs, deleting temporary files, and running malware scans cost nothing and solve slowness in most cases. Hardware upgrades like more RAM or an SSD cost money, but you only need them if software fixes don't help.