Apple says the AirTag battery will last about a year. When that time comes, it’s really easy to change the battery. AirTag uses a CR2032 battery, the kind of battery often found in remote controls and other handy devices. You can find them in most stores that sell batteries and they cost a couple of bucks each.
Update 7/28/21: Apple has posted a support document that points out that CR2032 batteries with bitterant coating may not work with AirTag. (Bitterant is added to some CR2032 batteries to discourage small children from handling them.) Check the battery’s packages before you make a purchase. (Hat tip to The Loop.)
In this video, learn how to change the AirTag battery. The instructions are listed below.
Open the AirTag by placing the white base facing downward. The Apple logo should face you.
Use two fingers, press down on two points beside the logo.
Turn the cap counter-clockwise. After the cap turns, you can take it off and change the battery.
Put the cap back on and turn the cap in the opposite direction to seal it.