Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I just tilted up my MacBook Pro to look at a piece of paper underneath it, and the lid touched a bottlecap on the table, clinging to it quite strongly. The whole top edge of the laptop (on the outside) is magnetized? What's this from?

share|improve this question
up vote 7 down vote accepted

The magnet in the clamshell activates a switch, in order to let the device know it should go to sleep.

This support article refers to the magnets in the clamshell:

share|improve this answer
HA, I love the resolution: Do not stack the computers. – Jakub Dec 8 '09 at 6:03

Depending on your model, the magnets are in different locations.

On the older style Aluminum MacBook Pros there are magnets to pull the latches down from above the monitor so it closes securely when you close the lid.

If you are using a Unibody MacBook Pro (current generation) then there are magnets around the display to help keep it closed and to trigger a switch to notify the computer to go to sleep.

share|improve this answer

The magnet is used in conjunction with a device called a Hall effect sensor in order to detect whether the lid is closed. Devices containing magnets, including many smartphones, may trigger this sensor and cause the system to sleep.

I can't help but laugh at this line (source):

For best results, do not stack computers.

share|improve this answer
Why was this post downvoted? – bwDraco Nov 16 '13 at 3:32
Upvoded for scientific reference – kinokijuf May 3 '14 at 9:51

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.