The short answer: A slow computer is almost always caused by one of four things — too many programs running at startup, not enough free storage space, too many browser tabs open, or it simply needs a restart. The fix for most slow computers takes less than 15 minutes and doesn't require technical skills or any money. Here's exactly what to do.
Do This First — It Fixes More Than You'd Expect
Restart your computer. Not sleep, not shut the lid — a full restart. Click Start (or the Apple menu on a Mac) > Restart.
If your computer hasn't been fully restarted in several days, this alone often makes a significant difference. Restarting closes every program running in the background, clears the temporary memory your computer uses, and gives everything a fresh start.
After restarting, open only the programs you actually need right now and test the speed again. If it's faster — great, come back and read the section on startup programs below so it stays fast. If it's still slow after a restart, the problem is something else and the next sections will help you find it.
The Four Reasons Computers Slow Down — And the Fix for Each
Reason 1 — Too Many Programs Starting Up When You Turn On Your Computer
Every time you install a program, it often adds itself to the list of things that start automatically when you turn on your computer. After a few years of installing apps, dozens of programs may be starting in the background every time you boot up — most of them things you never intentionally open. Each one uses a small amount of your computer's memory and processing power. Together, they can make your computer feel slow from the moment you turn it on.
How to fix it on Windows:
Press Ctrl + Shift + Esc to open Task Manager. Click the "Startup" tab at the top. You'll see a list of programs that start automatically and their "Startup impact" — Low, Medium, or High. Right-click on any program with "High" startup impact that you don't need immediately when you start your computer (things like Spotify, Discord, OneDrive, Steam, or any program you don't recognize) and select "Disable." You're not uninstalling anything — just telling it not to start automatically. You can still open these programs whenever you want.
How to fix it on Mac:
Click the Apple menu in the top left > System Settings > General > Login Items. You'll see two lists — "Open at Login" and "Allow in the Background." Review both and remove anything you don't need running constantly by selecting it and clicking the minus (−) button.
Restart your computer after making these changes. The startup time and overall speed improvement after cleaning up startup programs is often dramatic.
Reason 2 — Your Storage Is Almost Full
When your computer's hard drive or SSD is more than 85% to 90% full, your computer slows down significantly. This happens because your computer needs free storage space to run programs, save temporary files, and move data around — when there's very little free space, it has to work much harder to do the same tasks.
How to check how full your storage is:
On Windows: open File Explorer (the folder icon in your taskbar) > click "This PC" in the left column > look at your C: drive. The bar underneath it shows how full it is.
On Mac: click the Apple menu > About This Mac > More Info > Storage.
If your storage is over 85% full, freeing up space is the highest-priority fix.
What to delete to free up space quickly:
Start with your Downloads folder — most people have gigabytes of files here they downloaded once and never looked at again. Open your Downloads folder and delete anything you don't need.
Empty your Recycle Bin (Windows) or Trash (Mac). Files you've already deleted are still taking up space until you empty the bin.
On Windows, run Disk Cleanup: search for "Disk Cleanup" in the Start menu, open it, select your C: drive, and let it scan. It will show you how much space you can free up from temporary files, system files, and Windows updates. Click "Clean up system files" for a more thorough cleanup.
On Mac, go to Apple menu > System Settings > General > Storage > click "Recommendations." Mac will show you specific things taking up space and let you remove them in a few clicks.
If you need more space permanently: Consider moving photos and videos to an external hard drive or to cloud storage like Google Photos or iCloud. These files are often the largest category on a computer and are perfect candidates for cloud storage.
Reason 3 — Your Browser Is Using Too Much Memory
Your internet browser — Chrome, Edge, Firefox, Safari — is often the heaviest program running on your computer. Each browser tab uses memory, and some websites (especially ones with lots of videos, ads, or animations) use a surprising amount. If you habitually keep 20 or 30 browser tabs open at once, your browser might be using more memory than all your other programs combined.
The quick fix: Close browser tabs you're not actively using. Bookmark pages you want to come back to so you don't feel like you need to keep them open.
The specific fix for Chrome users: Chrome is known for using a lot of memory. Go to Chrome's settings (three dots in the top right corner > Settings > Performance) and enable "Memory Saver." This feature automatically puts inactive tabs to sleep, freeing up memory for the rest of your computer. The tabs are still there — they just reload quickly when you click on them.
Also check for browser extensions: Extensions (the small icons in the top right corner of your browser) each run constantly and use processing power. Click the extensions icon and review what you have installed. Remove any you don't use regularly.
Reason 4 — Your Computer Has Malware
If your computer is slow for no obvious reason — especially if it's also showing unexpected pop-up ads, redirecting you to strange websites, or behaving in ways that seem unusual — malware (unwanted software installed without your knowledge) may be running in the background.
On Windows: Windows Defender is built in and free. Search for "Windows Security" in the Start menu > Virus & threat protection > Quick scan. If it finds anything, follow the prompts to remove it.
On Mac: Macs are less frequently targeted by malware but not immune. Malwarebytes (malwarebytes.com) offers a free version that scans for Mac malware specifically.
If a scan finds and removes malware, restart your computer afterward and test the speed again.
"My Computer Is Slow Only When Doing Specific Things"
Slow only when connected to the internet: Your internet connection is the bottleneck, not your computer. Run a speed test at fast.com and see the earlier guide on slow internet if the results are low.
Slow only when a specific program is open: That program has a problem, not your computer. Try uninstalling and reinstalling it. If it's a browser, clear its cache (settings > Clear browsing data) and disable extensions one by one to find the culprit.
Slow mostly at startup but fine after 10 minutes: Startup programs are the cause. Follow the startup cleanup steps in Reason 1 above.
Slow all the time, even for simple tasks: Check your storage (Reason 2) and restart regularly. If the computer is more than 5 to 7 years old, the hardware itself may be reaching the end of its practical lifespan — at that point, the cost of upgrades sometimes exceeds the value of the computer.
The One Upgrade That Makes the Biggest Difference on an Old Computer
If your computer has a traditional spinning hard drive (not an SSD), replacing it with an SSD is the single most impactful upgrade you can make. Computers with SSDs start faster, open programs faster, and feel dramatically more responsive in every way.
You can tell whether your computer has an SSD or a spinning drive: on Windows, open Task Manager (Ctrl + Shift + Esc) > Performance > Disk. If it says "SSD" under the disk name, you already have one. If it says "HDD" or just shows a drive icon without "SSD," it's a spinning drive.
SSD upgrades for laptops cost $50 to $100 for the drive itself and can be done by any computer repair shop for an additional labor fee. The performance improvement on a computer with a spinning drive is transformative — an old slow computer can feel like a new machine after an SSD upgrade.
Pro Tip: Schedule a Monthly Restart and Storage Check
Set a recurring reminder on your phone for the first Saturday of every month. When it goes off, do three things: restart your computer, check your storage level (it should stay below 80% full), and close any browser tabs you've been meaning to close.
This small monthly habit prevents the gradual slowdown that comes from accumulated startup programs, a filling hard drive, and a browser that's been running for weeks without a break. Computers maintained this way stay noticeably faster over the years than ones that are only attended to when something goes wrong.
Last updated: July 2026. Steps apply to Windows 10, Windows 11, and macOS Ventura and later. Specific menu locations may vary slightly between versions.
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