The team behind Muun, a Bitcoin and Lightning wallet application available on Google Play, today announced that users can now make non-custodial Lightning payments. It requires zero channel configuration: all users need to do is make sure there are bitcoins in their wallet and scan the Lightning invoice to pay. Muun will automatically recognize it as an off-chain invoice and guide users all the way through the payment.

Under the hood is a payment flow which consists of a submarine swap. Submarine swaps allow users holding on-chain bitcoins to pay off-chain invoices through a swap provider. The swap provider doesn’t have custody of funds at any moment. This technology was created by Olaoluwa Osuntokun and Alex Bosworth from Lightning Labs.

Users will still have funds in one single wallet in Muun, and the whole payment process is the same as an on-chain payment, except for two differences: 1) most payments will be done instantly 2) different fees will appear in users transaction detail.

Users off-chain invoice will be paid instantly, except for very specific cases. Although there’s still an on-chain transaction involved in the swap, confirmations won’t be required in the vast majority of the cases, so the Lightning invoice will be paid instantly.

On the payment details screen, users will see two different fees: 1) “Lightning fee” are the routing costs of the off-chain component of the payment, and 2) “Swap fee”, includes the first on-chain transaction to the swap provider: