The idea: pay for the other participants
Every coinjoin has the same practical problem, and the project's README names it precisely: "A CoinJoin transaction requires other people to take part. The right resources (coins) have to be in the right place, at the right time, in the right quantity. This isn't a software or tech problem, it's an economic problem."
JoinMarket's answer was a market. Participants split into two roles. Makers keep coins online and wait, and say through an order book what fee they will accept to join. Takers want a coinjoin now and pay that fee. The README's own framing: "The takers pay a fee which incentivizes the makers. A form of smart contract is created, meaning the private keys will never be broadcasted outside of your computer."
That is a different shape from the coinjoin services that came before and after it. There was no operator collecting signatures and no service to shut down. The order book was public, and the README pointed users at mirrors of it, including Tor ones, while recommending that they run their own. A user who wanted the counterparties simply paid for them, and a user with idle coins could earn by supplying them.
The later versions added fidelity bonds, which make a sybil attack expensive by requiring a maker to lock coins in a timelocked output to gain weight in counterparty selection, and PayJoin under BIP78 for two-party payments that also break the common-input heuristic.
Structure and status
The code is under the GNU General Public License version 3. The earliest commits in the
original joinmarket repository are dated December 2014, and the current codebase,
joinmarket-clientserver, superseded it. No legal entity behind the project could be
established from any primary source. That is why structure reads Undocumented rather
than Unincorporated: the spec treats Unincorporated as a positive claim that no entity
exists, and not finding one is not the same as establishing there is none.
Both repositories are now archived. The README carries the notice: "THIS REPOSITORY IS NOW ARCHIVED. It is not recommended for use, though the releases are still available." Release 0.9.12, published on 21 April 2026, explains it: "Since the project has not been under active development for a considerable time, it is now being archived - the code and releases will remain in place, but there will be no further updates. Do not continue to use the code without having independent confidence that it is not exploitable; something we obviously cannot guarantee." The same note mentions a separate codebase, joinmarket-ng, and says explicitly that it is not a recommendation. This entry repeats that as written and adds nothing to it.
The project publishes no logo. The only images in the repository are interface screenshots, so no mark ships here and the page draws a monogram.