Merchant API

The mAPI (formally known as Merchant API) is a new development in Bitcoin, released in April 2020.

The API enables merchants accepting Bitcoin transactions to get all of the assurance they need to be able to accept transactions on a 'zero confirmation' basis (see Confirmation). Merchants are able to find out in advance (even before broadcasting a transaction) what transaction fee is required by Miners to mine it.

Background

As explained by Steve Shadders in Steve Shadders Discusses the Bitcoin SV (BSV) Tech Pillars - Bitstocks Podcast Ep. 7 at 36m 12s:

"If you can broadcast a transaction to miners and then get a response from them a second later, to say that they've accepted the transaction, then the 'zero conf' problem largely goes away".

It also allows Miners to put user-based fee policies in place. See The dawn of the age of competitive mining (Steve Shadders, yours.org, October 2019)

BRFC (Bitcoin Request for Comment) Specification

The BRFC specification can be found here.

Reference Implementation

The reference implementation can be found here.