This article explains how to put an Apple AirTag in Lost Mode using the Find My app on your iPhone, iPad, or Mac. It also shows you how to turn off Lost Mode once the AirTag is found.
How to Enable AirTag Lost Mode on a Lost or Stolen iPhone, iPad, and Mac
Lost Mode is one of the most essential AirTag features, as it helps you find items attached to an AirTag. To put an AirTag into this mode, you'll need to have your iPhone, iPad, or Mac handy.
Here's how to put an AirTag in Lost Mode on an iPhone. The steps are similar to using an iPad or Mac.
Open Find My on your iPhone.