CoinJoin vs Shared Send: Are They the Same Thing?
Two names for one underlying idea
If you've read about a shared send transaction, you may also have run into the term coinjoin and wondered whether they're different things. Mostly, they're not. Both describe the same basic move: several users combine their payments into a single Bitcoin transaction, instead of each sending a separate one.
The difference is mainly historical and terminological. CoinJoin is the general name for the technique, and it's the term used in technical references like the Bitcoin Optech coinjoin topic, which also documents the early "shared send" style implementations that popularized the idea. Shared send was the label some early wallet services put on their version of it. So it's reasonable to think of shared send as one branded flavor of coinjoin, the way "photocopy" and a copier brand name once described the same act.
Why combining transactions is even possible
Bitcoin's design makes this technique natural. A Bitcoin transaction is built from inputs (chunks of previously received bitcoin being spent) and outputs (the new destinations). Nothing in the rules says all the inputs must belong to one person. Each participant signs only their own inputs, so nobody in the group can spend anyone else's coins — the transaction only becomes valid once everyone whose inputs are included has signed. That's what lets strangers cooperate on one transaction without trusting each other with their money.
If you want a refresher on inputs, outputs, and signatures generally, start with what actually happens when you send a blockchain transaction.
What a coinjoin looks like on a block explorer
A typical single-user transaction has a small number of inputs and one or two outputs. A coinjoin instead shows:
- Many inputs, contributed by different participants
- Many outputs, often several of exactly the same size
The equal-sized outputs are deliberate. Since Bitcoin's ledger is public — the original Bitcoin whitepaper describes a system where all transactions are announced publicly while identities stay behind pseudonymous keys — anyone can see the transaction's structure. When several outputs are identical in amount, an outside observer looking at the chain can't tell from amounts alone which input funded which output. That ambiguity is the entire point of the construction.
If you're practicing on a real explorer, our guide to reading a transaction on a block explorer walks through the input and output panels this applies to.
So which term should you use?
- Say coinjoin when you mean the general technique — it's the standard term in current technical writing.
- Expect shared send in older articles, older wallet interfaces, and block-explorer help pages written in the ecosystem's earlier years.
- Either way, the object on the blockchain is the same thing: one ordinary, valid Bitcoin transaction with multiple participants' inputs and outputs inside it.
One last clarification: a coinjoin is not a special transaction type at the protocol level. The Bitcoin network doesn't flag or treat it differently — it's a regular transaction that happens to have a many-in, many-out shape. That's why the term describes a practice, not a feature switch you'll find in the protocol itself.