Computer Running Slow? Fixes for PC & Mac

A computer running slow is usually a software problem you can fix yourself: too many programs loading at startup, a nearly full drive, a browser stuffed with tabs, or one app quietly eating the processor. The built-in tools on Windows and macOS will show you what is dragging, and none of these fixes cost anything.

TL;DR

Restart the computer and install pending Windows or macOS updates first. It clears stuck processes and often fixes the problem on its own.
Open Task Manager (Ctrl + Shift + Esc) on Windows or Activity Monitor on a Mac and sort by CPU and memory to find the app hogging resources.
Turn off startup apps and login items you don’t need, and free up drive space with Storage Sense or the Mac’s Storage settings.
Run a scan with the built-in Windows Security app. Skip “PC cleaner” and registry-cleaner programs entirely.
If memory is constantly maxed out or the computer still has a spinning hard drive, an upgrade or replacement may be the real fix.

Why Your Computer Is Slow
Symptoms and Likely Causes
How to Speed Up a Slow Computer
What Not to Do
When to Call a Professional
How to Prevent It
FAQ

Why Your Computer Is Slow

Slowness almost always comes down to one of three resources running short: the processor (CPU), the memory (RAM), or the storage drive. Find which one is maxed out and you’ve found your cause.

It Hasn’t Been Restarted or Updated in a While

If you only close the lid, the computer may not have restarted in weeks, and stuck processes pile up. Microsoft notes that Windows updates often include performance fixes.

Too Many Apps Launch at Startup

Chat apps, cloud sync tools, game launchers, printer utilities, and update checkers often set themselves to open every time you sign in. Each one takes memory and processor time before you’ve opened anything. On a Mac these are called login items.

One App Is Hogging the CPU or Memory

A single misbehaving program, such as a frozen browser tab, a video editor rendering in the background, or a sync tool stuck in a loop, can pin the processor near 100%.

Not Enough RAM for What You’re Doing

When memory fills up, the computer starts swapping data back and forth between RAM and the storage drive, which is far slower. Apple explains that if an app needs more memory than your Mac has available, performance suffers.

The Storage Drive Is Nearly Full

Both Windows and macOS need free space on the main drive for temporary files, updates, and that memory swapping. A nearly full drive makes everything sluggish.

Browser Tabs and Extensions

Modern websites behave like full apps, so 40 open tabs can use more memory than everything else combined. Extensions add more load. If pages load slowly but the rest of the computer feels fine, the bottleneck may be your network instead; see our guide on how to fix slow Wi-Fi at home.

Malware or Adware

The FTC lists a computer that slows down, freezes, or crashes as a common sign of malware. Other clues include a changed browser home page, new toolbars, a flood of pop-up ads, and Task Manager or Activity Monitor refusing to open.

Overheating and Throttling

Processors protect themselves by slowing down when they get too hot. Dusty vents, soft surfaces, and hot rooms all contribute. Apple’s guidance is to use a Mac laptop where the room is between 50°F and 95°F and on a surface that allows airflow. For a deeper look, read our guide on why a laptop overheats and how to cool it down.

An Old Hard Drive or Aging Hardware

Older or budget computers may still use a spinning hard disk drive (HDD) instead of a much faster solid-state drive (SSD). Microsoft also notes that very old hardware may not improve much from tweaks, and upgrading can be the better long-term answer.

Symptoms and Likely Causes

Symptom	Likely cause	DIY or pro?
Slow for the first several minutes after turning on	Too many startup apps or login items	DIY
Fans loud while you’re doing nothing demanding	One process hogging the CPU, or blocked vents	DIY
Slows down as you open more tabs and apps	Not enough RAM	DIY first; pro if you need a RAM upgrade
“Low disk space” warning, updates failing	Drive nearly full	DIY
Pop-ups, new toolbars, changed home page	Adware or malware	DIY scan; pro if it keeps coming back
Gets slower the longer you use it, case feels hot	Overheating and throttling	DIY cleanup of vents; pro if fans fail
Slow everything, even after a fresh restart, on an older machine	Spinning hard drive or aging hardware	Pro for an SSD upgrade, or replace
Clicking or grinding noises, files that won’t open	Failing hard drive	Pro, and back up now

How to Speed Up a Slow Computer

Work through these in order, checking for improvement after each. You need no tools except compressed air and a soft brush for the vents.

Before you start: back up important files. A slow computer is sometimes a failing drive.

Step 1: Restart and Install Updates

On Windows, choose Start, then Power, then Restart. On a Mac, choose Apple menu, then Restart.

Then check for updates. On Windows, go to Settings, then Windows Update, and select Check for updates. On a Mac, go to Apple menu, then System Settings, then General, then Software Update.

Step 2: Find the Resource Hog

On Windows, press Ctrl + Shift + Esc to open Task Manager. On the Processes tab, click the CPU column header to sort by processor use, then do the same for Memory and Disk. If an app you aren’t using is near the top, select it and choose End task.

On a Mac, open Activity Monitor from Applications, then Utilities. The CPU tab shows each app’s processor use. To close a stuck app, select it and click the stop button at the top of the window.

Only end processes you recognize as apps you opened. Ending system processes can crash the computer or lose unsaved work.

Step 3: Check Whether You’re Out of Memory

In Task Manager, the Performance tab shows Memory as a percentage. If it stays close to full during your normal work, with only your usual apps open, you’re running short.

On a Mac, open the Memory tab in Activity Monitor and look at the Memory Pressure graph at the bottom. Apple says green means memory is being used efficiently, yellow means your Mac might eventually need more RAM, and red means it needs more.

Step 4: Turn Off Startup Apps and Login Items

On Windows, open Task Manager, select Startup apps, right-click anything you don’t need right away, and choose Disable. Leave antivirus and hardware driver entries alone.

On a Mac, go to Apple menu, then System Settings, then General, then Login Items. Select an app under “Open at Login” and click the minus button to remove it. In the same window, you can turn off “Allow in the Background” for apps that don’t need to work while closed.

Step 5: Free Up Storage Space

On Windows, go to Settings, then System, then Storage. Under Storage Sense, choose Run Storage Sense now to clear temporary files and the Recycle Bin.

On a Mac, go to Apple menu, then System Settings, then General, then Storage, and review the recommendations. Apple says macOS can move files to iCloud and help you spot files you no longer need.

While you’re there, uninstall programs you never use. On Windows, that’s Settings, then Apps, then Installed apps; on a Mac, drag unused apps from the Applications folder to the Trash.

Step 6: Tame Your Browser

Close tabs you aren’t actively using, or bookmark them for later. Then open your browser’s extensions or add-ons page and remove anything you don’t use or don’t recognize.

Step 7: Scan for Malware

On Windows, open Settings, then Privacy & security, then Windows Security, then Virus & threat protection, and select Quick scan. If you still suspect a problem, Microsoft recommends the Microsoft Defender Antivirus offline scan under Scan options. It restarts the computer, so save your work first.

If you find malware, the FTC advises staying out of banking and shopping accounts until the device is clean, then changing your passwords and turning on two-factor authentication. On a Mac, install all macOS updates and remove any apps or browser extensions you didn’t knowingly install.

Step 8: Check for Heat and Clean the Vents

Safety: shut the computer down completely and unplug the power adapter before cleaning. Don’t open the case of a laptop, and don’t spin the fan blades with compressed air.

Use short bursts of compressed air at the outside vents, holding the can upright, and brush lint from the openings. Then set the laptop on a hard, flat surface like a desk instead of a couch or bed.

Step 9: Adjust Windows Performance Settings

Search Start for “Adjust the appearance and performance of Windows,” open it, and choose Adjust for best performance on the Visual Effects tab.

On a laptop, Settings, then System, then Power & battery has a Power mode menu. Best performance speeds things up, but Microsoft warns it drains the battery faster and makes the device run warmer.

Step 10: Check the Disk on a Mac

Apple suggests opening Disk Utility (in Applications, then Utilities), selecting your startup disk, and using First Aid to check for and repair disk errors. If First Aid reports problems it can’t fix, back up immediately and plan for a repair.

What Not to Do

Don’t install “PC cleaner,” “Mac cleaner,” memory booster, or registry-cleaner programs. The built-in tools already do the useful parts, and many of these programs nag you to pay or bundle in unwanted software.
Don’t call a phone number in a pop-up that says your computer is infected. The FTC warns that tech support scammers use fake warnings to get remote access and charge for problems that don’t exist.
Don’t end processes you don’t recognize in Task Manager or Activity Monitor. Look up the name first.
Don’t delete files from Windows or System folders to free space. Use Storage Sense, Disk Cleanup, or the Mac’s Storage settings instead.
Don’t run two antivirus programs at once. They conflict and slow the computer further.

When to Call a Professional

Get help from the manufacturer, an authorized service provider, or a reputable local repair shop if you notice any of these:

Clicking, grinding, or buzzing from inside the computer, or files that suddenly won’t open. These can mean a failing drive, so back up first.
Disk Utility First Aid or Windows reports drive errors it can’t repair.
Fans that never stop, never start, or rattle, or a case that’s too hot to touch comfortably during light use.
Malware that returns after scans, or Task Manager and Activity Monitor won’t open.
Memory pressure stays yellow or red, or Windows memory sits near full, even with only a few apps open.
The computer still has a spinning hard drive and you’d like an SSD upgrade.

Before you pay for a RAM upgrade, check whether it’s even possible. On a Mac, hold Option, choose Apple menu, then System Information, and click Memory under Hardware. If there’s no Upgradeable Memory section, the RAM can’t be added to.

Weigh repair against replacement. If the computer can’t run the current version of Windows or macOS, has soldered memory that’s already maxed out, or would need several parts replaced, a new machine is often the better spend. Get a written quote and compare it to a new computer’s price.

How to Prevent It

Restart at least once a week instead of only closing the lid.
Leave automatic updates on for the operating system and your browser.
Turn on Storage Sense in Windows so it clears temporary files automatically, and keep a healthy chunk of your drive free.
Review your startup apps, login items, and browser extensions every few months.
Use the laptop on a hard surface and blow dust out of the vents a couple of times a year.
Download software only from the developer’s own site or the official app store.

FAQ

Why is my computer so slow all of a sudden?

A sudden slowdown usually means something new is using resources: an update installing in the background, a newly installed app, a stuck browser tab, or malware. Open Task Manager or Activity Monitor and sort by CPU to see what’s at the top.

Does adding more RAM make a computer faster?

Only if you’re running out of memory now. If Task Manager shows memory near full or Activity Monitor’s memory pressure is yellow or red, more RAM will help. If memory has plenty of room, extra RAM won’t change much, and many newer laptops can’t be upgraded anyway.

Will a PC cleaner or registry cleaner speed up my computer?

No, skip them. Windows and macOS already include tools to clear temporary files, manage startup apps, and scan for malware.

How do I know if my computer has a virus?

Warning signs include sudden slowness or crashes, a changed browser home page, new toolbars, lots of pop-up ads, and system tools that won’t open. On Windows, run a Quick scan and then an offline scan in Windows Security. Never trust a pop-up that tells you to call a number for help.

Is it worth fixing an old slow computer or should I buy a new one?

Try the free fixes first, since they solve most slowdowns. If the computer still has a spinning hard drive and otherwise works well, an SSD upgrade from a repair shop can extend its life. If it can’t run current operating system updates or needs multiple parts, replacing it usually makes more sense.

Computer Running Slow? How to Speed Up a Windows PC or Mac