What is an atomic swap?
An atomic swap is a trade between two blockchains where both sides settle or neither does. Cryptography, not a middleman, guarantees that no one can take the other person's coins without giving their own.
The word "atomic" comes from computing, where an atomic operation can't be half-finished. In a crypto atomic swap, two people each lock their coins in a way that is linked by a shared secret. Revealing the secret to claim one side automatically makes it possible to claim the other. If nobody claims in time, a time-lock returns each person's coins.
How Monero atomic swaps work
Classic atomic swaps use hash time-locked contracts (HTLCs), small scripts that release coins when someone reveals a secret before a deadline. Bitcoin supports these scripts. Monero doesn't, because its privacy design leaves out that kind of scripting.
XMR–BTC atomic swaps work around this with adaptor signatures. In simplified form:
- The Bitcoin seller locks BTC in a Bitcoin script with two paths: a claim path for the buyer and a refund path after a time-lock.
- The Monero seller sends XMR to an address whose private key is split between both parties, so neither can spend it alone.
- When the Monero seller claims the BTC, the signature they publish on the Bitcoin chain reveals the missing half of the Monero key.
- The Bitcoin seller uses that half to take the XMR. If something stalls, the time-locks allow refunds.
Open-source projects such as COMIT's xmr-btc-swap, UnstoppableSwap and BasicSwap implement this protocol. They typically take 30 to 60 minutes or more, because both chains need confirmations and the parties exchange several messages.
Limits and risks of atomic swaps
Atomic swaps remove the middleman, but they come with their own practical limits:
- You must stay available. If a swap stalls, you need to come back before the time-lock expires to claim a refund. Miss the window and the protocol may let the other side punish you or keep the coins, depending on the implementation.
- Liquidity is thin. You need a counterparty, called a maker, willing to trade the amount you want at that moment. Large or very small amounts can be hard to fill.
- Software is specialized. Most tools are run by small open-source teams. Some need a local wallet or node, and the user experience varies.
- Fees can add up. Bitcoin transactions for locking, claiming and refunding each pay a network fee, and makers set their own spread.
None of this makes atomic swaps unsafe. It means they reward users who are comfortable with the technology.
A short history
Atomic swaps were proposed for Bitcoin-like coins in 2013 and first used between chains that share the same scripting system, such as Bitcoin and Litecoin. Monero was harder because it can't run hash time-locks. A protocol based on adaptor signatures, published by Joël Gugger (h4sh3d) in 2020, made XMR–BTC atomic swaps practical, and several open-source projects have built on it since.
How instant exchanges work
An instant exchange is simpler for the user. You choose a pair, enter your receiving address and send a deposit. The service converts your coins and sends the other coin to your address. This is how QuietSwap works.
The trade-off is trust: while your deposit is being converted, the exchange holds it. A good instant exchange reduces that risk with clear fees, refund addresses, address validation and a short holding time.
Atomic swap vs instant exchange: side by side
| Atomic swap | Instant exchange | |
|---|---|---|
| Who holds your coins | Nobody. The protocol enforces settlement. | The exchange, during the swap. |
| Ease of use | Needs dedicated software, sometimes command line | A web form and a deposit address |
| Availability | Needs a counterparty online with liquidity | Always available |
| Typical time | 30–60+ minutes | 20–60 minutes for XMR–BTC |
| If something fails | Time-lock refund; you must come back to claim it | Refund to the address you provide |
| Fees | Network fees plus the maker's spread | Service fee plus network fee (QuietSwap: 1%) |
Which should you use?
Choose an atomic swap if…
You want zero counterparty risk, you're comfortable running specialized software, and you can stay online until the swap finishes.
Choose an instant exchange if…
You want a simple web flow, guaranteed availability, address checks and support if something looks wrong.
Both are valid ways to move between Monero and Bitcoin. If you go with an instant exchange, swap XMR to BTC or swap BTC to XMR on QuietSwap with the full fee breakdown shown before you send.
Atomic swap FAQ
Is QuietSwap an atomic swap?
No. QuietSwap is an instant exchange: you send a deposit and we send the other coin. We explain atomic swaps here so you can choose the model that suits you.
Are Monero atomic swaps possible?
Yes. Monero has no scripting for hash time-locks, so XMR–BTC atomic swaps use adaptor signatures on the Bitcoin side combined with a shared key on the Monero side. Open-source tools such as UnstoppableSwap and BasicSwap implement this.
Are atomic swaps faster than instant exchanges?
Usually not. Both sides wait for confirmations on both chains and the protocol has several rounds, so they typically take 30 to 60 minutes or more.
What happens if an atomic swap fails?
Time-locks let each party take back their own coins after a deadline. Users must stay online or come back before the deadline to claim a refund.