What is Destination Tag / Memo?

A destination tag, called a memo on some networks, is a short number or code sent alongside a crypto deposit address so the receiving platform can tell which customer the incoming transaction belongs to. It exists because exchanges and casinos often pool many users behind one shared address; the address says where the coins go, and the tag says whose account to credit. Networks that use tags or memos usually display them next to the deposit address with a warning to include them. Sending without the required tag, or with someone else's tag, does not reverse itself: the transfer confirms on chain but lands unassigned, and recovery depends on a manual support process that may take time or may not be possible.