Why are there multple transactions on a single transaction id?

in bitcoin basics , Transactions and UTXOs, the teacher shows you can have a single transaction id with bitcoin beingsent to multiple wallets, should that make it 2 seperate transactions? Can someone explain?

No because you can have multiple inputs to a tx. UTXOs are Unspend TX Outputs that you can use as inputs into a new transaction and it can as well have multiple outputs (usually it has at least two).

Transaction inputs can come from many addresses or even wallets from many users. This is a so called CoinJoin tx where many users sign a single transaction. The benefit for doing this is lower fees and better privacy. :slight_smile:


Is that something bit coin algorithm does automatically? It sounds like it batches transactions together but how does it work if it is taking Inputs from different addresses and combining them, it sounds hard to keentrqck.

Yes, modern wallets do this behind the scenes its not something a user should be concerned with. If you use a hardware wallet you might have noticed you get a different address each time you want to receive funds.
Once you send them the wallet will pick the UTXOs and sign them when constructing a new tx.