Common reasons your computer slows down

A slow computer usually comes from one of four sources: too many programs running at once, a hard drive that is nearly full, malware or viruses, or an aging processor that cannot keep up with newer software. The good news is that most of these have straightforward fixes you can do yourself in under an hour.

The most common culprit is startup programs—applications that launch automatically when you turn on your computer and sit in the background using memory and processing power. Many programs install themselves to start this way without asking. If your computer is slow only after you have been using it for a while, or if it is slow right after startup, startup programs are likely the problem.

A second major cause is a full or nearly full hard drive. When your storage drive has less than 10 to 15 percent free space, Windows and Mac both slow down noticeably because they cannot write temporary files smoothly. This is especially true if you have large video files, photo libraries, or old backups taking up space.

Key Takeaways

  • Disable startup programs through your system settings—most computers have dozens of apps launching automatically that you never use.
  • Check how much free space remains on your hard drive; if it is below 10 percent, delete or move large files to an external drive.
  • Run a malware scan using Windows Defender (built into Windows) or a free tool like Malwarebytes to rule out infections.
  • Close browser tabs and background applications before opening heavy programs like video editors or games.
  • Restart your computer regularly—it clears temporary files and resets memory that programs may be hoarding.

How to disable startup programs on Windows

Open the Task Manager by pressing Ctrl + Shift + Esc on your keyboard. Click the "Startup" tab at the top. You will see a list of programs set to launch when Windows starts, along with a column labeled "Status" showing which ones are currently enabled.

Right-click any program you do not need to start automatically—common offenders are Adobe Reader, Spotify, Discord, OneDrive, and printer software. Select "Disable" from the menu. You can always launch these programs manually when you need them. Restart your computer to see the difference. Most users find their startup time cuts in half after disabling 5 to 10 unnecessary programs.

Do not disable anything labeled "Windows" or with a publisher name you do not recognize—these are usually system files your computer needs. If you are unsure about a program, search its name online before disabling it.

How to disable startup programs on Mac

Click the Apple menu in the top-left corner and select "System Settings." Go to "General" and then click "Login Items." You will see two lists: "Allow in the Login Window" and "Open at Login." The second list is what slows down your startup.

Select any program in the "Open at Login" list and click the minus button below it to remove it. Like Windows, you can always open these programs manually. Common Mac startup programs that slow things down are Dropbox, Google Drive, Slack, and web browsers.

Freeing up hard drive space

Right-click your main hard drive (usually called "C:" on Windows or "Macintosh HD" on Mac) and select "Properties" on Windows or "Get Info" on Mac. Look for the amount of free space listed. If it shows less than 10 percent of your total drive size, you need to delete or move files.

Start by emptying your Recycle Bin (Windows) or Trash (Mac)—files you delete do not actually disappear until you empty these folders. Then look for large files you no longer need: old video projects, duplicate photos, or installation files for programs you have already installed. You can also move large photo or video libraries to an external hard drive or cloud storage like Google Drive or OneDrive.

On Windows, you can also use the built-in Disk Cleanup tool. Press the Windows key, type "Disk Cleanup," and open it. Select your main drive and click "OK." Check the boxes next to "Temporary files," "Recycle Bin," and "Temporary internet files," then click "Delete Files." This usually frees up several gigabytes.

Checking for malware and viruses

Malware and viruses can slow your computer dramatically by running hidden processes in the background. Windows comes with a built-in tool called Windows Defender that scans for these threats. Press the Windows key, type "Windows Defender," and open "Windows Security." Click "Virus & threat protection" and then "Scan options." Select "Full scan" and click "Scan now." A full scan takes 30 minutes to an hour but is thorough.

If you want a second opinion, read the free version of Malwarebytes from malwarebytes.com. Install it, open the program, and click "Scan." Let it run to completion. If either tool finds threats, follow the on-screen instructions to remove them and restart your computer.

Do not pay for antivirus software unless you have a specific reason—Windows Defender is sufficient for most users, and Malwarebytes free version catches what Defender misses. Avoid downloading antivirus tools from pop-up ads or unknown websites, as these are often scams.

Closing background applications and browser tabs

Open the Task Manager (Ctrl + Shift + Esc on Windows) or Activity Monitor (Command + Space, type "Activity Monitor" on Mac) to see what is running right now. Look at the "Memory" or "CPU" column to see which programs are using the most resources. If you see something using 20 percent or more of your CPU or memory and you are not actively using it, close it.

Browser tabs are a hidden culprit—each open tab uses memory, and some websites run heavy scripts that consume CPU power. If you have 20 or 30 tabs open, close the ones you are not actively reading. Many browsers have extensions that can suspend inactive tabs automatically, which helps if you tend to keep many tabs open.

When to restart your computer

Restarting clears your computer's memory and stops programs from hoarding resources. If your computer is slow but you have not restarted it in several days or weeks, a restart often fixes the problem when ready. Make it a habit to restart at least once a week, or nightly if you use your computer heavily.

If your computer is still slow after trying all of these steps, the problem may be hardware-related—your hard drive may be failing, your RAM may be defective, or your processor may straightforward be too old for the software you are running. At that point, consider taking your computer to a repair shop for a diagnosis, or if the computer is more than 5 to 7 years old, it may be time to replace it.

Frequently Asked Questions

How do I know if my hard drive is failing?

A failing hard drive often makes clicking or beeping sounds, takes a very long time to open files, or freezes randomly. If you hear unusual noises, back up your files to an external drive or cloud storage when ready and take your computer to a repair shop. A failing drive can stop working without warning.

Will disabling startup programs break anything?

No. Disabling startup programs only prevents them from launching automatically—you can still open them manually whenever you need them. The only exception is system programs labeled "Windows" or "Apple," which you should leave alone.

Is it safe to delete files from my Downloads folder?

Yes, if you have already installed the programs or used the files. Your Downloads folder often fills with old installers and files you no longer need. Check what is there, delete anything you recognize as old, and empty your Recycle Bin or Trash afterward.

Can I speed up my computer by adding more RAM?

If your computer is using 90 percent or more of its RAM constantly, adding more can help. Open Task Manager (Windows) or Activity Monitor (Mac) and check the memory usage. If it is consistently high even after closing programs, more RAM may improve speed. However, this requires opening your computer, so consider having a technician do it.

Why does my computer slow down after a few hours of use?

Programs often leak memory over time, meaning they use more and more RAM the longer they run without being closed. Restarting your computer clears this. If slowdown happens within an hour or two, a specific program may be the problem—check Task Manager or Activity Monitor to see what is using the most memory.