Not safe for kids under 18
Grindr is a dating app that markets towards gay, bi, trans, and queer people. Users can upload and browse profile pictures and bio descriptions and directly message one another. Sexual/Mature content is likely.

In-depth breakdown

Minimum Age Requirement
Messaging Capabillities
Users can send messages directly to other active users in their area, including photo, audio, and video messages.
Location Sharing
Location is used to connect users within a certain radius.
Parental Controls
None, though Apple and Android parental controls could be used at the device level.
Grindr has a reputation for being a “hookup” app that facilitates sexual encounters between queer men.