The most common reasons your PC slows down
A slow PC 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 processor and memory that are being overloaded by what you are trying to do. Most of the time it is not a hardware failure—it is something you can see and fix yourself by looking at what is actually running.
The first step is to figure out which of these is your problem. A PC that takes two minutes to start up but runs fine once it is open has a startup problem. A PC that slows down only when you open certain programs has a memory or malware problem. A PC that is slow all the time, even when nothing is open, usually has a full hard drive or a virus.
Key Takeaways
- Check your startup programs in Task Manager (Windows) or Activity Monitor (Mac) to see what is loading when your PC turns on—most of these can be disabled without breaking anything.
- A hard drive that is more than 80 percent full will slow down your PC noticeably, and clearing out old files or uninstalling programs you do not use can free up space quickly.
- Malware and unwanted browser toolbars often hide in your system and consume memory and processing power; a scan with Windows Defender (built into Windows) or Malwarebytes can find them.
- If your PC is old and you are running new software, your processor and RAM may straightforward be too weak for the job, and upgrading RAM is usually cheaper than buying a new machine.
Too many programs starting when your PC boots
Every program you install wants to run automatically when you turn on your computer. Email clients, messaging apps, cloud storage, antivirus software, and manufacturer utilities all sit in your startup queue. Each one takes a few seconds to load, and if you have twenty of them, your PC will take five minutes to be usable.
On Windows, open Task Manager by pressing Ctrl+Shift+Esc. Click the Startup tab. You will see a list of programs with a Status column that says Enabled or Disabled. Right-click any program you do not need running all the time—Spotify, Discord, Dropbox, Adobe updates—and select Disable. You do not need to uninstall them; they will still open when you click them, they just will not load automatically.
On Mac, go to System Settings, then General, then Login Items. You will see a list of apps that open at startup. Click the minus sign next to any you want to remove from the list. The apps stay on your computer; they just will not launch automatically anymore.
Your hard drive is too full
When your hard drive is more than 80 percent full, Windows and Mac both slow down because they need free space to write temporary files while programs are running. You can check how full your drive is in seconds. 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 are above 80 percent, start by emptying the Recycle Bin (Windows) or Trash (Mac)—deleted files still take up space until you empty it. Then look for large files you do not need: old video files, installation files for programs you already installed, duplicate photos, or downloads you finished with months ago. Moving these to an external hard drive or cloud storage frees up space without losing them.
If you are still full after that, uninstall programs you do not use. On Windows, go to Settings > Apps > Apps & Features, find the program, and click Uninstall. On Mac, open Applications, drag the program to Trash, then empty Trash. This usually frees up several gigabytes.
Malware or unwanted software is running in the background
Malware, browser hijackers, and unwanted toolbars consume processor power and memory without you knowing they are there. They often come bundled with free software downloads or hide in browser extensions. A slow PC combined with unexpected pop-ups, a changed search engine, or a new toolbar in your browser is a sign something unwanted is installed.
Windows 10 and 11 come with Windows Defender built in. Open Windows Security (search for it in the Start menu), click Virus & threat protection, then click Scan options. Select Full scan and click Scan Now. This takes 20 to 60 minutes but will find most malware. If Defender finds something, follow the prompts to remove it.
For a second opinion, read Malwarebytes (the free version is fine). Install it, open it, and click Scan. It will find things Defender missed sometimes. Restart your PC after any scan that finds threats. If your PC is very slow and you suspect malware, run both scans.
Your processor or RAM cannot handle what you are running
If your PC is five or more years old and you are trying to run modern software—video editing, 3D games, or dozens of browser tabs with video playing—your processor and memory may straightforward be too weak. You can check what is using your resources in Task Manager (Windows) or Activity Monitor (Mac).
On Windows, open Task Manager (Ctrl+Shift+Esc), click the Performance tab, and look at CPU and Memory percentages. If either is above 80 percent when you are not doing anything demanding, something is wrong. Click the Processes tab and sort by Memory or CPU to see what is using the most. If it is a program you recognize and do not need, close it or uninstall it. If it is a system process you do not recognize, search the name online before closing it.
On Mac, open Activity Monitor (search for it in Spotlight), click the Memory tab, and look at the Memory Pressure graph at the bottom. If it is in the yellow or red zone, your Mac does not have enough RAM for what you are doing. Closing browser tabs and programs will help temporarily, but upgrading RAM is the permanent fix if you do this work regularly.
Your hard drive is failing or fragmented
Hard drives (the spinning kind, not solid-state drives) slow down as they age and as files get scattered across the disk. If your PC is very slow even after you have cleaned it up, disabled startup programs, and scanned for malware, your hard drive may be wearing out.
On Windows, you can defragment your drive to help. Open Settings, search for Defragment, and click Defragment and Optimize Drives. Select your C: drive and click Optimize. This can take an hour or more but will speed things up if fragmentation is the problem. If your PC is still slow after that, the drive itself may be failing and you should back up your files and consider replacing it.
On Mac, defragmentation is not usually necessary because the system handles it automatically. If your Mac is slow and you have tried everything else, the hard drive may be failing. Back up your files to an external drive or cloud storage and take it to an Apple Store or a Mac repair shop to have the drive checked.
Your internet connection is slow, not your PC
Sometimes a PC feels slow because the internet is slow, not because the computer itself is struggling. If your PC is fast when you are working offline but slow when you are browsing or streaming, the problem is your connection, not your machine.
Run a speed test at speedtest.net to see what your internet speed actually is. If it is much slower than what you pay for, restart your router (unplug it for 30 seconds, then plug it back in). If that does not help, contact your internet provider. If your speed test is fine but websites still load slowly, the problem may be your browser or an extension. Try opening the same website in a different browser to see if it is faster.
Frequently Asked Questions
How do I know if my PC has a virus?
Signs include unexpected pop-ups, a changed search engine or homepage, new toolbars in your browser, or your PC running very slowly even when nothing is open. Run a full scan with Windows Defender or Malwarebytes to check. If either finds threats, follow the prompts to remove them and restart your PC.
Will disabling startup programs break anything?
No. Disabling a startup program just means it will not load automatically when your PC turns on. You can still open it by clicking it whenever you want. If you disable something and realize you need it to start automatically, you can re-enable it in Task Manager the same way.
How much free space should I have on my hard drive?
Keep at least 15 to 20 percent of your drive free. If your drive is 500 GB, that means keeping at least 75 to 100 GB empty. This gives Windows and Mac room to write temporary files and keeps your PC running smoothly.
Is it worth upgrading RAM instead of buying a new PC?
If your PC is three to five years old and the only problem is that it runs out of memory, upgrading RAM is usually much cheaper than a new computer. RAM costs $30 to $100 depending on how much you add. If your PC is older than that or has other problems, a new machine may be the better choice.
Why is my PC slow only when I open certain programs?
That program is using more memory or processor power than your PC has available. Close other programs and browser tabs before opening it. If it is always slow, the program may need more RAM or a faster processor than you have, or it may have a bug. Check the program's website to see the minimum requirements.