Q: My laptop fan is running constantly even when I am not doing anything demanding. What is actually going on

[Shane]

This comes up constantly so a proper answer is worth pinning. A laptop fan running at high speed when idle almost always means something is consuming CPU or GPU resources that you cannot see at a glance. The culprit in 2026 is most often a background process, an update service, a browser with a bad extension, or a cloud sync catching up after a large file change.

Q: How do I find what is causing it?

A: Windows: Task Manager sorted by CPU then by GPU. Look for anything above 5 percent that is not something you intentionally have running. Mac: Activity Monitor, same sort. Linux: htop or btop. If you see a browser process near the top, disable extensions one at a time. If you see a system process, Google the exact name before killing it

[Badger27]

The browser extension angle catches people off guard. A bad extension can peg a CPU core and most people never think to check

[IronQuarry98]

Chrome running multiple renderer processes for background tabs with autoplay video is the one I diagnose for people most often

[Coastal Otter]

On Windows the Windows Update service doing background indexing or the antivirus doing a scheduled scan are the two most common innocuous culprits

[RayOfLight]

Malware is also still a thing. If Task Manager shows high CPU from an unfamiliar process with a random looking name that is a different conversation

[Dylan]

The Intel and AMD power management interaction with Windows 11 has caused phantom fan activity on some laptops. Check the power plan settings before concluding it is a process issue

[Sparrow]

Thermal paste degradation on older laptops causes the CPU to throttle and the fan to compensate. If the machine is more than four years old this is worth ruling out

[Ronan_34]

HWInfo64 on Windows gives you the actual temperature readings so you know whether the fan is reacting to genuine heat or a software issue

[Rachel93]

Yeah that is about right. That is just how it is.

Ha, fair enough.

A lot of Windows issues sort themselves with a fresh install of drivers

[Finley_19]

On Mac the Kernel Task process consuming high CPU is usually the system protecting itself from overheating rather than an actual runaway process. Counterintuitively the fix is to cool the machine not kill the task

[Wendy5]

This should be in a tech help FAQ. Pinning it