What is the ruling on using matchmaking apps or online ta'aruf?

Permissible if used to look for a spouse in a way that observes the limits of the Shariah and safety.
An app is only a tool; its ruling depends on how it is used. Use it to share basic biodata and identify candidates, then involve the wali or family as soon as possible. Avoid prolonged private conversations, photos that do not cover the ʿawrah, and meeting alone. Beware of love scams: do not transfer money, do not share personal photos or documents, and verify identity through a chaperoned video call and family meetings. Women should also confirm the man's true marital status. See criteria.