Why Your CPU Usage Is High (Near 100%) With Nothing Running (8 Main Reasons)

The CPU handles all of the basic math that makes every program and process on your PC work. While it can handle some intensive tasks, it shouldn’t always be high, or near 100% usage. So when it is at this point for extended periods of time, is there an obvious reason for it?

Your CPU usage can spike to nearly 100% out of nowhere. This can be caused by Task Manager glitches, background processes, malware, and even your antivirus software. The best way to fix these issues is to go through the programs in Task Manager and investigate which are using too much CPU power.

In the guide below, I cover the top 8 things to check when CPU usage is high, but if you’re still experiencing slowness, I also published a video that dives into 16 further things you can check:

Your CPU has a lot of responsibilities when it comes to running your PC. Let’s see if we can lighten the load.

8 Reasons Your CPU Usage Is High

Your CPU usage percentage will occasionally get high. This can be during resource intensive tasks, or while you have too many background processes running. This is typically normal and not much cause for concern.

However, when your CPU never seems to settle down or the high usage is costing you performance, you should check out these eight common causes of high CPU usage.

Task Manager Errors And Glitches

When you first open Task Manager, you’ll likely see a few huge spikes across the board. This is the normal behavior of Windows Task Manager. Task Manager occasionally has display errors that cause it to display incorrect values for everything from CPU usage to memory.

Task Manager is very reliable and useful for spot checking and controlling your CPU temperature. However, Task Manager is also notorious for being a little buggy. This is at its worst when you first launch it.

The CPU section of Windows Task Manager showing various CPU spikes on some threads
The CPU section of Windows Task Manager showing various CPU spikes on some threads (especially when first launched)

This shouldn’t be a big cause for alarm. It’s just one of those quirks of Windows technology that has persisted for years of Windows releases. If your Task Manager displays are incorrect for anything more than a few seconds at launch, you might need to conduct a system restoration or a Windows reinstall.

Background Processes

Your CPU is essentially the brain of your computer. It is busy running all of the core math that structures all computer processing. Every single program you run uses some of your CPU’s processing power.

This means that having too many processes running in the background can eat up your CPU. This could be caused by anything from too many open tabs in your favorite web browser to a bunch of open, but minimized, programs.

Performance tuning and gaming peripheral management software can also be spiking your CPU usage. These programs typically stay active even when not in use and can contribute to higher than desired CPU usage numbers.

While you have the Task Manager open, you can look at all of the programs that are currently using CPU power. If you have never launched Task Manager before, it will open in “minimized” view:

A basic Windows Task Manager without extra details being shown
A basic Windows Task Manager without extra details being shown

This only shows the actively running programs. But if you click on “More details”, you will then see the full list of processes – including background processes:

Windows Task Manager showing active and background processes
Windows Task Manager showing active and background processes

Feel free to give any of these back processes a break if you’re not currently using them… just be careful not to accidentally shut down vital programs like System or Windows Explorer—which is also used as your file browser.

When in doubt, search the name of an unknown program to make sure it’s safe to shut down.

Buggy Software

In an ideal world, all software would consume a reasonable amount of your CPU’s power, but every now and then there is a program that sponges up all of your computer’s processing leaving you trying to figure out what’s going on. There is a history of otherwise reliable programs that regularly cause CPU usage spikes.

While any program can spike CPU usage if it experiences a glitch, we should talk about the biggest culprit on your Windows PC.

Google’s Chrome web browser might be easy to use and packed with useful features, but it is also a notorious CPU hog. Even when Chrome isn’t being buggy, it can suck up your CPU worse than glitching software. Here’s a tip for mitigating this resource hungry browser: uninstall it.

Just kidding. You should regularly close open Chrome tabs. The bookmark feature on any browser is there to save your CPU from running all those websites at once. You should also manage your Chrome extensions and regularly update your browser to keep your CPU from struggling to lift a browser that can use more CPU processing power than some games.

Malware and Viruses Spike CPU Usage

This is one of the scariest causes of CPU usage spikes. Malware and viruses are often used to hijack your computer’s processing power. This almost always causes dramatic spikes in your CPU use.

Malware programs and other cybersecurity threats can be used to transform your computer into anything from a hacker’s personal cryptocurrency mining rig (known as cryptojacking), or a bot in their botnet. This will drive your CPU usage through the roof!

The best way to fight this is to practice good cybersecurity. These tips will keep your PC free of malware and CPU power stealing viruses.

  • Always keep your passwords up-to-date and avoid using common passwords
  • Stick to safe websites that use the “HTTPS” standard (indicated by a padlock in the address bar)
  • Never open an attachment that you don’t recognize
  • Keep your antivirus software up-to-date
  • Run malware and virus sweeps to get rid of any suspect programs and files
A MalwareBytes Premium scan for malware and viruses
A MalwareBytes Premium scan for malware and viruses

Antivirus Software (And Settings)

So, we just talked about how viruses and malware can ruin your CPU’s performance, but the antivirus software you rely on can also wreck your CPU usage. This software keeps you safe, but sometimes you need to keep it in check to make sure it’s not worse than the malware it fights.

This comes down to the settings of your antivirus software. This software regularly performs tasks in the background that use a lot of power. These are normally fine, but if they are set too high then you can see some performance loss across your PC.

If your antivirus software has been eating up your CPU, then head into the settings. You should lower the frequency of scans, manage settings, and take a look at how you’ve configured your firewall. The more active your antivirus software has to be, the more CPU usage it’s going to take up.

Processing Intensive Programs and Tasks

Your CPU can spike when you use software that just consumes more power than most. This is typically normal to see and shouldn’t cause any long term issues.

There are a variety of programs that use lots of CPU power. Video editing, 3D modeling, and processor intensive tasks can all cause notable spikes in processing, but they should stop once you’re done with the current task that is causing the spike.


Gaming is resource intensive on your RAM, graphics cards, and your CPU. The more gaming performance you pull out of your PC, the higher your CPU usage is going to go:

A game Serious Sam 4 taking up over half of the CPU on a Ryzen 5900X CPU
A game Serious Sam 4 taking up over half of the CPU on a Ryzen 5900X CPU

This shouldn’t be a problem. A PC built for gaming can handle high CPU usage for gaming sessions. However, if your CPU usage is getting so high that it’s impacting your performance, there are a few things to do.

Before we get to the extreme measures, like dropping graphics settings, we need to talk about the other programs that often go with gaming.

Live streaming, chats, and screen recording tech is very resource intensive. The same is true for programs that run alongside your games like speed running software that tracks splits and parsing software for MMORPG players. These programs can be cut back, or just used when needed, to give your CPU some extra wiggle room.

Then there are the games themselves. We all want 4k with 120 frames per second and the highest ray tracing settings, but our CPU’s might not want all that. If your favorite games are using too much CPU power, consider picking and choosing the graphics settings that matter most to you while bringing the others down to more efficient settings.

High CPU Temperatures and Dust

Asus armory crate showing CPU temp at 62 degrees celsius
Asus armory crate showing CPU temp at 62 degrees celsius

We often think of CPU usage in terms of software. This is pretty reasonable given that it’s software that makes up most of our CPU usage problems. However, your CPU is a physical device that can suffer from physical problems.

Your CPU has one big, physical enemy that gates how much performance you can squeeze out of your tech. The name of this CPU power thief is: heat.

A CPU that is regularly too hot is going to have much less power than the exact same CPU, and computer setup, that has adequate heat mitigation. If your CPU is overheating, even simple processes can trash your usage percentage. So, what’s causing your CPU to overheat?

The first thing to check is your heat mitigation. Is your CPU’s fan properly seated and running normally? If so, you’re good to move onto the next thing to check.

Dust is one of the biggest problems when it comes to heat mitigation. Dust gets into every computer sooner or later and causes all kinds of problems. Dust naturally insulates which means the more dust is in your computer, the hotter things get.

Use a can of compressed air to remove dust from around your fans and especially remove any dust that is building up on the physical components themselves. A layer of dust on your CPU is essentially a little blanket keeping it nice and toasty.

cropped A picture of me Tristan
About Tristan Perry

Tristan has been interested in computer hardware and software since he was 10 years old. He has built loads of computers over the years, along with installing, modifying and writing software (he's a backend software developer 'by trade').

Tristan also has an academic background in technology (in Math and Computer Science), so he enjoys drilling into the deeper aspects of technology.

Tristan is also an avid PC gamer, with FFX and Rocket League being his favorite games.

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