Your computer is probably running too many programs at once, or your hard drive is nearly full

A sudden slowdown usually means one of three things: background programs are consuming your processor or memory, your storage drive is running out of space, or malware has installed itself without your knowledge. The good news is that you can check each of these yourself in a few minutes, and most fixes take less than an hour. Start by looking at what is running in the background, then check your disk space, then scan for malware if the first two do not explain the problem.

The slowdown happened suddenly because something changed on your system recently—a new program installed, an update ran, or a file grew too large. Your computer did not just wear out. That means you can usually reverse it by undoing that change or removing what is taking up the resources.

Key Takeaways

  • Open Task Manager (Windows) or Activity Monitor (Mac) to see which programs are using the most CPU and memory right now.
  • Check your available disk space by right-clicking your main drive and selecting Properties (Windows) or Get Info (Mac)—if you have less than 10 percent free, your computer will slow down.
  • Restart your computer before trying anything else, because programs left running in the background often clear out after a reboot.
  • If slowness started after installing a new program, uninstall it to see whether that was the cause.
  • Run a malware scan using Windows Defender (built into Windows) or a third-party scanner if you suspect infection.

Check what programs are running right now

Open Task Manager on Windows by pressing Ctrl + Shift + Esc, or right-click the taskbar and select Task Manager. On a Mac, press Command + Space, type Activity Monitor, and press Enter. Look at the CPU and Memory columns to see which programs are using the most resources.

If you see a program using 50 percent or more of your CPU or memory, that is your culprit. Common offenders are web browsers with many tabs open, video conferencing software, cloud backup programs running in the background, and antivirus software doing a full scan. If the program is something you do not recognize, search its name online to find out what it does—it may be a component of a program you installed months ago.

Close any program you do not need right now. If a program keeps reappearing in Task Manager even after you close it, it is set to launch automatically when your computer starts. You can disable this by going to Settings > Apps > Startup (Windows) or System Preferences > General > Login Items (Mac) and unchecking the program.

Restart your computer

Before you do anything else, restart your computer. This clears out temporary files, stops programs that are stuck in memory, and often solves slowness that appeared overnight. Shut down completely—do not just put it to sleep—and wait 30 seconds before turning it back on.

If the slowness goes away after a restart, a program was probably running in the background and consuming resources. If it comes back after a few hours, that program is launching again automatically, and you should disable it in your startup settings as described above.

Check how much disk space you have left

On Windows, right-click your C: drive (or whichever drive holds your operating system) and select Properties. Look at the pie chart at the bottom. On a Mac, click the Apple menu, select About This Mac, then click Storage. Your computer needs at least 10 to 15 percent of your drive free to run smoothly. If you have less than that, your computer will slow down noticeably because it cannot create temporary files or cache data efficiently.

If your drive is nearly full, delete files you no longer need. Start with your Downloads folder, your Recycle Bin (Windows) or Trash (Mac), and any large video or photo files you have backed up elsewhere. You can also move files to an external drive or cloud storage to free up space. If you cannot find enough to delete, consider buying an external hard drive or upgrading to a larger internal drive.

Check the size of your largest folders by right-clicking them and selecting Properties (Windows) or Get Info (Mac). Often a single folder—like your Documents or Pictures folder—is taking up most of the space, and you can move old files out of it to reclaim gigabytes quickly.

Scan for malware

Malware can slow your computer by running hidden programs, stealing your internet bandwidth, or consuming processor power to mine cryptocurrency. On Windows, open Windows Defender (built into Windows 10 and 11) by typing "Windows Defender" in the search box and clicking "Virus & threat protection." Click "Scan options," select "Full scan," and click "Scan now." This takes 30 minutes to an hour depending on how much is on your drive.

On a Mac, malware is less common, but you can still scan using a free tool like Malwarebytes. read it, install it, and run a full scan. If either scan finds malware, follow the prompts to remove it and restart your computer.

If you do not want to wait for a full scan, run a quick scan first. Windows Defender offers a "Quick scan" option that checks the most common locations where malware hides and usually takes 5 to 10 minutes. If the quick scan finds nothing, you can assume malware is not the problem.

Look at your browser if web pages load slowly

If your computer feels fast but web pages load slowly, the problem is probably your browser or your internet connection, not your computer itself. Close all browser tabs except one and try loading a page. If it loads quickly, you have too many tabs open. If it still loads slowly, restart your router by unplugging it for 30 seconds and plugging it back in.

If restarting your router does not help, check whether your browser has accumulated too many extensions. Open your browser's extension or add-on menu and disable any you do not recognize or use regularly. Some extensions consume a lot of memory and slow down page loading. You can also try clearing your browser cache by going to Settings > Privacy > Clear browsing data (or the equivalent in your browser) and selecting "All time."

Check for recent Windows or macOS updates

If your computer slowed down right after an update, the update itself may be the cause. Windows and macOS sometimes release updates that have bugs or that are not optimized for older hardware. Check whether an update ran recently by going to Settings > Update & Security > Windows Update (Windows) or System Preferences > Software Update (Mac) and looking at the update history.

If an update ran recently and you believe it caused the slowdown, you can try rolling back to the previous version. On Windows 10, go to Settings > System > Recovery and click "Go back." On Windows 11, go to Settings > System > Recovery and click "Go back" under Previous version of Windows. On a Mac, you cannot easily roll back, but you can restart in Safe Mode (hold Shift while restarting) to see whether the slowdown persists—if it does not, a third-party program is the problem, not the update.

Frequently Asked Questions

My computer is slow but Task Manager shows nothing using much CPU or memory. What else could it be?

Check your disk space first—if your drive is nearly full, your computer will feel slow even if no single program is using much CPU. If disk space is fine, the slowness may be caused by a failing hard drive. On Windows, type "Check Disk" in the search box and run the Check Disk utility. On a Mac, restart while holding Command + S to enter Single User Mode and run fsck -fy at the prompt. If either tool reports errors, your drive may be failing and you should back up your files when ready.

I disabled a startup program and now my computer will not start. How do I fix it?

Restart your computer in Safe Mode, which loads only essential programs. On Windows, restart and press F8 repeatedly before the Windows logo appears, then select Safe Mode. On a Mac, restart and hold Shift. Once in Safe Mode, go back to your startup settings and re-enable the program you disabled. Then restart normally.

How often should I restart my computer to keep it running fast?

Restarting once a week is a good habit, especially if you leave your computer on all the time. Restarting clears out temporary files and stops programs from accumulating in memory. If your computer feels slow, restart before trying anything else—it solves the problem about half the time.

Is it normal for a computer to slow down as it gets older?

Yes, but not because the hardware wears out. Older computers slow down because you have installed more programs, accumulated more files, and your drive is fuller. You can keep an older computer running fast by regularly deleting files you do not need, disabling startup programs, and running malware scans. If your computer is more than five years old and still feels slow after these steps, upgrading your RAM or replacing your hard drive with a solid-state drive (SSD) can make a big difference.

My computer is slow only when I use a specific program. Is that program broken?

Probably not—the program likely just needs more resources than your computer has available. If the program is a web browser, close other programs and tabs. If it is something else, check Task Manager to see how much memory and CPU it is using. If it is using more than 80 percent of your available resources, your computer does not have enough memory for that program, and you may need to upgrade your RAM or use a lighter alternative.