what type of battery does an airtag take

An Apple AirTag uses a CR2032 lithium 3V coin battery. This battery type is chosen for its long-lasting lithium chemistry and ability to operate in extreme temperatures. The battery is widely available at electronic stores and pharmacies. It needs to be replaced approximately every 12 to 18 months depending on usage. When replacing, the positive side of the CR2032 battery should face up. Some CR2032 batteries have a bitterant coating to discourage ingestion, but these may not always work well with AirTags, so it is recommended to use ones labeled "Compatible with Apple AirTag" or without the bitterant coating.