What actually slows a computer down, and what you can fix right now

A slow computer usually comes from one of four things: too many programs running at startup, a hard drive that is nearly full, malware or unwanted software, or a hard drive that is failing. You can check and fix the first three yourself in under an hour. The fourth requires a replacement drive, which a repair shop can do for $100 to $300.

Start by checking how much free space you have on your 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 percent of your drive free, that is your main problem — your computer cannot write temporary files, so everything slows down. Deleting old files, uninstalling programs you do not use, and moving large media files to an external drive will fix this when ready.

Next, look at what starts when you turn on your computer. Every program that launches at startup uses memory and processing power before you even open anything. Most of these you did not choose to start.

Key Takeaways

  • A nearly full hard drive is the most common cause of slowness — if you have less than 10 percent free space, delete files and uninstall unused programs first.
  • Disable startup programs through Task Manager on Windows or System Settings on Mac; most of these run without your knowledge and drain memory.
  • Malware and unwanted toolbars slow your browser and computer — run a scan with Malwarebytes or Windows Defender to check for infections.
  • Closing browser tabs and limiting open programs reduces memory use; if your computer still crawls after these steps, the hard drive may be failing and needs replacement.

Disable programs that start automatically when you turn on your computer

On Windows 10 and 11, press Ctrl+Shift+Esc to open Task Manager. Click the Startup tab. You will see a list of programs that launch when Windows starts. Most of these you did not install intentionally — they came bundled with software or installed themselves. Right-click any program you do not use every day and select Disable. Common culprits are Adobe Reader, Spotify, Discord, Slack, and various manufacturer utilities.

On Mac, go to System Settings, then General, then Login Items. You will see two lists: Apps and Allow in the Login Window. Remove anything from the first list that you do not need running constantly. The second list controls which apps can run in the background even when closed — disable those too unless you specifically need them.

Restart your computer after disabling startup programs. You should notice the boot time drop when ready, and your computer will have more memory available while you work.

Check for malware and unwanted browser extensions

Malware, adware, and browser hijackers slow your computer and steal your data. They often install without your knowledge when you read software from untrusted sources or click misleading ads. Run a full scan with Windows Defender (built into Windows) or Malwarebytes (free version available). On Mac, Malwarebytes is also the most reliable option.

To scan with Windows Defender, type "Windows Security" in the Start menu, open it, click Virus & threat protection, then click Scan options. Select Full scan and click Scan now. This takes 30 minutes to an hour. Malwarebytes works faster — read it, install it, and click Scan. Either tool will find and remove most infections.

While you are at it, check your browser extensions. In Chrome, click the three dots in the top right, go to Extensions, and remove anything you do not recognize or use. In Firefox, click the menu button (three horizontal lines), select Add-ons, then Extensions, and remove unwanted items. Malicious or poorly written extensions slow your browser and steal data.

Delete files you no longer need and move large media to external storage

Once you know how much free space you need, start deleting. Begin with your Downloads folder — most people leave old installers and files there for months. On Windows, open File Explorer and navigate to Downloads. On Mac, open Finder and click Downloads in the sidebar. Delete anything you have not used in the last month.

Next, look at your Documents, Pictures, and Videos folders. Move large video files, photo libraries, and old project folders to an external hard drive or cloud storage like Google Drive or OneDrive. You can still access them, but they will not take up space on your computer. If you have old backups, system restore points, or duplicate files, delete those too.

On Windows, the Disk Cleanup tool can help. Type "Disk Cleanup" in the Start menu, select your C: drive, and click OK. Check the boxes for Temporary files, Recycle Bin, and Old Windows installations, then click Delete Files. This usually frees up several gigabytes.

Close unnecessary browser tabs and limit open programs

Each open browser tab uses memory, and some websites run heavy scripts that consume CPU power. If you have 20 tabs open, your computer has to manage all of them even if you are only looking at one. Close tabs you are not actively using. If you find yourself keeping tabs open to remember to do something later, use a bookmark folder or a to-do app instead.

The same applies to programs. Running Photoshop, Spotify, Discord, and a video call at the same time will slow any computer. Close programs you are not using. On Windows, you can see what is using the most memory by opening Task Manager (Ctrl+Shift+Esc), clicking the Performance tab, then clicking Open Resource Monitor. On Mac, open Activity Monitor (Applications > Utilities > Activity Monitor), click the Memory tab, and sort by Memory to see what is using the most.

Update Windows or macOS and your drivers

Outdated operating systems and drivers can slow your computer and create security holes. On Windows, go to Settings, click Update & Security, then Windows Update, and click Check for updates. Install any updates and restart. On Mac, click the Apple menu, select System Settings, click General, then Software Update, and install any available updates.

Drivers are software that let Windows and macOS talk to your hardware — your graphics card, network adapter, and other components. Outdated drivers can cause slowness 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.

When to replace your hard drive

If you have done all of the above and your computer is still slow, your hard drive may be failing. Hard drives wear out after 3 to 5 years of regular use. Signs of failure include clicking or grinding noises, files taking a very long time to open or save, and the computer freezing randomly.

You can check the health of your drive on Windows using a free tool like CrystalDiskInfo. read it, install it, and run it. If it shows a red or yellow status, your drive is failing. On Mac, Disk Utility can check drive health — open Applications > Utilities > Disk Utility, select your drive, and click First Aid. If it reports errors, your drive is failing.

A failing drive needs to be replaced. Take your computer to a repair shop — they will back up your files, install a new drive, and reinstall your operating system. This costs $100 to $300 depending on the drive size and your location. A solid-state drive (SSD) is faster than the older mechanical hard drives and will make your computer noticeably quicker overall.

Frequently Asked Questions

How do I know if my computer is slow because of software or hardware?

Open Task Manager on Windows (Ctrl+Shift+Esc) or Activity Monitor on Mac (Applications > Utilities). Look at CPU and Memory usage. If both are below 50 percent when you are not doing anything, the slowness is likely a full hard drive or a failing drive. If CPU or Memory is consistently above 80 percent, a program is using too many resources — find it in the list and close it or uninstall it.

Will clearing my cache and temporary files speed up my computer?

It will free up a small amount of space, but it is not a major speed boost. Clearing browser cache in Chrome, Firefox, or Safari takes a few minutes and might free up 100 MB to 1 GB. It is worth doing if you are low on space, but it is not the first thing to try. Focus on deleting old files and disabling startup programs first.

Should I use a cleaning app or optimization software?

Most cleaning and optimization apps do not help and some are malware. Avoid them. Windows Defender and the built-in tools in Windows and macOS are enough. If you want a second opinion on malware, Malwarebytes is legitimate, but do not pay for a subscription — the free version scans and removes infections.

Does adding more RAM make my computer faster?

It can help if your computer is constantly running out of memory, but it is expensive and not always necessary. Check Activity Monitor on Mac or Task Manager on Windows to see if Memory is consistently above 80 percent. If it is, more RAM will help. If not, a full hard drive or startup programs are the problem, and adding RAM will not fix them.

How often should I restart my computer?

Restarting once a week clears temporary files and resets memory, which can help keep your computer running smoothly. You do not need to do it every day, but if your computer feels sluggish, a restart is often the quickest fix. It takes a few minutes and costs nothing.