What's actually slowing your computer down

A slow computer usually isn't broken—it's just doing too much at once. Your hard drive or solid-state drive (SSD) fills up, background programs launch automatically when you start up, your browser collects years of cached files, or malware and dust inside the machine force your processor and cooling fan to work harder. The good news is that most of these problems you can fix yourself in an afternoon, and the fixes cost nothing.

Before you start, restart your computer. This clears temporary files from memory and stops programs that are stuck running in the background. If the slowness disappears after a restart, you probably just had too many things open at once. If it comes back within an hour, one of the problems below is the real culprit.

Key Takeaways

  • Restarting your computer clears temporary memory and stops stuck background programs, which solves slowness in many cases.
  • Uninstalling programs you don't use and disabling startup programs in Task Manager (Windows) or System Preferences (Mac) frees up resources when ready.
  • Clearing your browser cache, cookies, and temporary files can recover gigabytes of storage and speed up web browsing noticeably.
  • Checking your hard drive or SSD for viruses using Windows Defender (built into Windows) or your Mac's built-in security tools catches malware before it drains performance.
  • If your hard drive is more than 85 percent full, deleting old files or moving them to external storage will restore speed faster than any other single fix.

Check how full your hard drive is and delete what you don't need

A hard drive or SSD that is more than 85 percent full runs slowly because the system has no room to write temporary files. On Windows, right-click your C: drive in File Explorer, select Properties, and look at the pie chart. On Mac, click the Apple menu, select About This Mac, then click Storage. If the bar is mostly full, you need to delete files.

Start by moving old photos, videos, and documents to an external hard drive or USB stick. These files take up the most space. Then use the Disk Cleanup tool on Windows (search for it in the Start menu) to remove temporary files, old Windows updates, and the Recycle Bin. On Mac, use the Storage settings to see what's taking up the most room, then delete applications you no longer use by dragging them to the Trash.

If you have gigabytes of old downloads, browser caches, or duplicate files, clearing those out can free up 10 to 50 gigabytes or more. The speed improvement is often dramatic once you drop below 80 percent full.

Stop programs from launching when your computer starts

Every program you install tries to run automatically when you turn on your computer. Most of them you never use, but they sit in memory consuming resources. On Windows, open Task Manager by pressing Ctrl+Shift+Esc, click the Startup tab, and look at the list. Right-click any program you don't need running in the background and select Disable. Common culprits are Adobe Reader, Spotify, Discord, and Zoom—they all launch themselves unless you tell them not to.

On Mac, go to System Preferences (or System Settings on newer versions), click General, then Login Items. Remove anything you don't recognize or don't need running all the time. Disabling startup programs won't uninstall them—you can still open them manually whenever you want. This change takes effect the next time you restart.

Reducing startup programs by even five or six can cut your boot time in half and free up memory for the programs you actually use.

Clear your browser cache and temporary files

Your web browser stores copies of every webpage, image, and video you visit so it loads faster next time. Over months and years, this cache grows to several gigabytes and can slow down both your browser and your entire computer. Clearing it takes two minutes and is safe—websites will just take a few seconds longer to load the first time you visit them after clearing.

In Chrome, Firefox, or Edge, press Ctrl+Shift+Delete (Windows) or Command+Shift+Delete (Mac) to open the Clear Browsing Data window. Select All Time, check Cached Images and Files, and click Clear Data. Do the same for Cookies and Other Site Data if you want to fully reset your browsing, though this will log you out of websites.

If you use Safari on Mac, go to History menu, click Clear History, select All History from the dropdown, and click Clear History. Clearing your cache can recover 1 to 5 gigabytes of space and noticeably speed up web browsing.

Scan for viruses and malware

Malware and viruses run hidden in the background, consuming processor power and bandwidth. Windows comes with Windows Defender built in—search for Windows Defender in the Start menu, click Virus & Threat Protection, and run a Full Scan. This takes 30 minutes to an hour but catches most common infections. On Mac, your system has built-in malware protection, but you can also run a scan by going to System Preferences, clicking Security & Privacy, and reviewing the security status.

If you suspect a serious infection, read and run Malwarebytes (the free version is sufficient for a one-time scan). Restart your computer in Safe Mode first—on Windows, restart and press F8 repeatedly during startup; on Mac, restart and hold Shift. Safe Mode loads only essential programs, making it easier for antivirus software to find and remove threats.

A full virus scan can take an hour, but if malware is present, removing it often restores 20 to 30 percent of your computer's speed when ready.

Uninstall programs you don't use

Every installed program takes up disk space and can run background processes. On Windows, go to Settings, click Apps, then Apps & Features. Scroll through the list and uninstall anything you haven't used in months. Click the program name and select Uninstall. On Mac, open Applications in Finder, select a program, and drag it to the Trash, or use the Uninstall option if the program provides one.

Pay special attention to trial software, games, and duplicate programs (like having both Chrome and Edge if you only use one). Uninstalling 10 to 20 unused programs can free up 5 to 20 gigabytes depending on what they were.

Update your operating system and drivers

Windows and Mac release updates that patch security holes and improve performance. On Windows, go to Settings, click Update & Security, and select Check for Updates. On Mac, go to System Preferences (or System Settings), click General, then Software Update. Let the updates install and restart your computer if prompted. This usually takes 15 to 30 minutes but can noticeably improve speed and stability.

Outdated drivers—the software that controls your graphics card, network adapter, and other hardware—can also slow your system. On Windows, right-click the Start menu, select Device Manager, and look for any devices with a yellow warning triangle. Right-click those devices and select Update Driver. Most of the time Windows will find the latest version automatically.

When to call a professional

If your computer is still slow after trying these steps, the problem may be a failing hard drive, overheating from dust buildup inside the case, or a hardware issue that requires opening the machine. A computer technician can diagnose the problem with diagnostic software and clean internal dust, replace a failing drive, or upgrade your RAM if your computer is running out of memory.

If your computer is more than five years old and still slow after these fixes, upgrading to a newer machine or adding an SSD (if you have an older computer with a traditional hard drive) is often more cost-effective than repeated repairs.

Frequently Asked Questions

Will clearing my cache delete my passwords and saved logins?

Not if you uncheck "Cookies and Other Site Data" when clearing. Clearing only cached images and files leaves your passwords intact. If you want to clear everything, write down your passwords first or use your browser's password manager to back them up.

Is it safe to disable all startup programs?

Yes, with one exception: do not disable Windows Update or your antivirus software. Everything else can be disabled without breaking your computer. If you disable something and notice a problem, you can re-enable it the same way.

How often should I clear my browser cache?

Once every three to six months is typical. If your browser feels sluggish or you're running low on disk space, clear it more often. You can also set your browser to clear the cache automatically every time you close it in the settings menu.

What's the difference between a hard drive and an SSD?

A hard drive uses spinning magnetic disks and is slower but cheaper. An SSD has no moving parts and is much faster. If you have an older computer with a hard drive, upgrading to an SSD is one of the biggest speed improvements you can make, though it requires opening the computer or paying a technician to install it.

Can dust inside my computer actually slow it down?

Yes. Dust clogs the cooling fan and heatsinks, causing your processor to overheat and throttle (run slower to avoid damage). If your computer sounds like a jet engine, it's probably overheating. You can carefully use compressed air to blow dust out of the vents, but if you're not comfortable opening the case, a technician can do it safely.