Mac fan always running or loud: find the cause
Why a Mac's fan runs all the time, how to find the process or condition behind it, and when the fan itself needs service.
Why is my Mac fan always running?
The fan follows heat, and heat follows work. A process using CPU in the background, indexing after an update, a hot room or blocked vents all keep it spinning.
How do I find what is causing it?
Activity Monitor, CPU tab, sorted by % CPU. Anything high while you are idle is the cause: find what is using the CPU.
When is it the fan itself?
If CPU is low, the Mac is cool and the fan is still loud, or it grinds or rattles, the fan may need cleaning or service.
Common questions
Why is my MacBook fan so loud when nothing is open?
A background process or post update indexing is usually busy. Sort Activity Monitor by CPU.
Can I turn off the fan on my Mac?
No, and you should not. Reduce the load or heat instead.