Windows running slow: common causes and how to fix it
Identify the most common causes of slowdowns and get your computer back up to speed, step by step.
If your computer takes longer and longer to open programs, or freezes whenever you do anything, you don't always need to reinstall Windows. Most of the time the problem has a specific cause — and an equally specific fix.
The most common causes
Before applying any fix, it's worth figuring out what's actually going on. These are the causes that come up again and again:
- Too many programs launching automatically when Windows starts.
- The hard drive is almost full (less than 10-15% free space).
- A mechanical hard drive (HDD) instead of an SSD.
- Not enough RAM for the number of programs you run at once.
- Malware or background processes eating up resources.
How to check: open Task Manager
(Ctrl + Shift + Esc) and look at the "Performance" tab. If the
disk is sitting at 90-100% usage without you doing anything special, that's
usually the first clue.
Step-by-step fixes
1. Trim your startup programs
In Task Manager, go to the "Startup" tab and disable anything you don't need the moment you turn the PC on (chat apps, app store helpers, manufacturer utilities, and so on).
# See which programs launch with Windows, from PowerShell
Get-CimInstance Win32_StartupCommand | Select-Object Name, Command, Location
2. Free up disk space
Use Disk Cleanup (search for "cleanup" in the Start menu) or go to Settings → System → Storage → Temporary files.
Tip: if your system drive is regularly almost full, consider moving to a larger SSD. You'll notice a bigger difference than from any software tweak.
3. Rule out malware
Run a full scan with Windows Defender (or your antivirus of choice) before going further. An unknown process quietly eating CPU in the background is a very common cause of sudden slowdowns.
Warning: be wary of third-party "miracle cleaner" tools that promise to speed up Windows automatically. Some delete files you actually need or bundle in unwanted extra software.
When the problem is the hardware
If your PC is still slow after all of the above, the bottleneck is probably your RAM or the drive itself. Our guides on RAM and SSD vs HDD will help you decide what's worth upgrading.
Note: this guide gets updated as we test new Windows 11 versions and optimization tools.
Frequently asked questions
Will reinstalling Windows fix the slowdown?
Often yes, since it clears out accumulated programs and startup entries — but it's worth trying the fixes in this guide first: they're much faster and don't risk your files.
How much RAM do I need for Windows 11 to run smoothly?
For everyday use (browsing, office apps, a handful of tabs) 8 GB is the recommended minimum, and 16 GB if you do photo/video editing or run several heavy programs at once.
Does third-party antivirus slow things down more than Windows Defender?
It depends on the antivirus, but Windows Defender is very well optimized for the system it runs on. If you notice slowdowns after installing third-party antivirus, check its real-time scan settings.