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A Mac with a mind of its own

A couple of times, my M1 MacBook Pro seems to have started up on its own. I have its startup chime enabled, and have heard it sound when the case has still been closed. Does this mean it’s defective?

No. What has probably happened is that a magnet in an iPad cover or something similar has triggered the sensor which tells your MacBook Pro that its case has been opened. This seems to occur most commonly with M1 models, although it can affect older ones too.

Rather than use a mechanical sensor, which will eventually break, Apple’s notebook models use a magnetic sensor to detect when their case is opened. This is usually on the left side of the case. Bringing another magnet close to that can fool that sensor into thinking that the case has been opened, and it triggers the Mac to start up,