What is photoanalysisd and why is it using so much CPU?

2018-01-22 17:00

If you open Activity Monitor and see photoanalysisd using 50 to 100 percent of your CPU, do not worry. It is a normal macOS process, and it will calm down.

What does it do?

photoanalysisd is the daemon that scans your photo library using machine learning. It goes through every photo and video to:

Spot faces (for the People album)
Recognise objects, scenes, and places
Sort photos for Memories and smart search
Find text in images

All of this happens on your device, not on Apple's servers. When you search for "dog" or "beach" in the Photos app and get results, photoanalysisd made that possible.

Why is it using so much CPU?

Running machine learning on thousands of photos is heavy work. The process works hardest:

After a macOS upgrade, when it often needs to re-scan your whole library with updated models
After importing many photos, since new photos need scanning
When you first turn on iCloud Photos, as all downloaded photos get scanned

How long does it take?

It depends on the size of your library. A few thousand photos might take a few hours. A large library with tens of thousands can take a day or more. The process slows itself when you are using your Mac and speeds up when it is idle.

Can you stop it?

You can force quit it in Activity Monitor, but it will restart and carry on where it left off. There is no way to stop it for good without turning off the Photos features it powers.

The best thing to do is leave your Mac plugged in and let it finish. Once the first scan is done, photoanalysisd only runs briefly when new photos arrive.

Should you worry?

No. It is doing useful work and will finish on its own. Your Mac might feel warm and the fans might spin up for a while, but that is normal during the first scan.

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