B:// file

B:// Unspendable

A file on chain: the data, its media type, its encoding and an optional name, under the B prefix.

What it is

B is a Bitcom protocol for storing a file in an OP_RETURN output. Its prefix is a Bitcoin address, 19HxigV4QyBv3tHpQVcUEQyq1pzZVdoAut, and the fields after it are fixed in order. Any page or app can then load the file by its transaction id.

Script pattern

OP_FALSE OP_RETURN A data output.
"19HxigV4QyBv3tHpQVcUEQyq1pzZVdoAut" The B prefix.
<data> The file's bytes.
<media type> Such as image/png or text/markdown.
<encoding> Such as binary or utf-8.
<filename> Optional.
"|" … Optional: a pipe, then another protocol such as MAP or AIP.

How it is spent

It cannot be spent.

Background

unwriter published B in 2019 as one of the first Bitcom protocols, alongside tools that served B files straight to the browser. It became the common way to put images, pages and media on chain, and other protocols pipe into it.

On chain

8af3c6f02d50ef71a0b9e281cfb5a32860452bf9af7d25c3ba0a66bc6e392d78 block 957,679
fd4c02466488f70de87232795864349449edb6c561a234dd40015601d3fd9922 block 957,679
5aba22a3690e7ddd1da0b0274c9746cc31cfb96cd2593c46e32b955ebcf824ea block 957,679
8ea61f0810c4c1ef323ae376bb554453af5ed520b6cf8481d823bec4bfbce643 block 957,679
dad2e641455f2809f8b9ca68d05482aaebde6d226ee9c20dba6980dec486fe67 block 957,679

Transactions our protocol detector tagged B://. Transaction pages need sign-in.

Specification

B:// specification
See B in the Bitcom registry
/api/v1/types/b
/api/v1/txs?type=b every stored tx of this type, newest first, with an API key or signed in.