Tutorials

BIP21

Bitcoin Cash is all about sending and receiving payments. BIP21 describes a way to encode payment request information such as address, amount, message etc as a URI. These URIs are a very popular way to share payment requests and you’ll often see them as links in a website or as QR codes. Today we’re releasing encodeBIP21 and decodeBIP21 to make it easy for your app to encode/decode BIP21 $BCH URIs.

encodeBIP21

To encode a BIP21 URI pass in the address as the first argument and an object of options as the 2nd argument. encodeBIP21 will encode the options object as query string parameters. This works for addresses encoded in cashAddr w/ and w/out prefix and legacy base58Check.

// cashaddr w/ prefix
let address = 'bitcoincash:qrdsfshx7yzfjl9sfj2khuja5crcu4vaxqrt2qkz5s'
let options = {
  amount: 1,
  label: '#BCHForEveryone',
}
BITBOX.BitcoinCash.encodeBIP21(address, options)
// bitcoincash:qrdsfshx7yzfjl9sfj2khuja5crcu4vaxqrt2qkz5s?amount=1&label=%23BCHForEveryone

// cashaddr w/out prefix
let address = 'qrdsfshx7yzfjl9sfj2khuja5crcu4vaxqrt2qkz5s'
let options = {
  amount: 1,
  label: '#BCHForEveryone',
}
BITBOX.BitcoinCash.encodeBIP21(address, options)
// bitcoincash:qrdsfshx7yzfjl9sfj2khuja5crcu4vaxqrt2qkz5s?amount=1&label=%23BCHForEveryone

// works w/ legacy addresses too
let address = '1LPqVeYx4Xa96NYCm4X3jhGhPf2EY6ygna'
let options = {
  amount: 1,
  label: '#BCHForEveryone',
}
BITBOX.BitcoinCash.encodeBIP21(address, options)
// bitcoincash:qr2tcpvsnca0gaw7jxngtmsvd4ffqdpkxqtfzcd8w3?amount=1&label=%23BCHForEveryone

Error handling

encodeBIP21 won’t accept strings or negative values as an amount.

// won’t accept a string as an amount
let address = 'bitcoincash:qrdsfshx7yzfjl9sfj2khuja5crcu4vaxqrt2qkz5s'
let options = {
  amount: 'one',
  label: '#BCHForEveryone',
}
BITBOX.BitcoinCash.encodeBIP21(address, options)
// TypeError: Invalid amount

// won't accept a negative value as an amount
let address = 'bitcoincash:qrdsfshx7yzfjl9sfj2khuja5crcu4vaxqrt2qkz5s'
let options = {
  amount: -1,
  label: '#BCHForEveryone',
}
BITBOX.BitcoinCash.encodeBIP21(address, options)
// TypeError: Invalid amount

decodeBIP21

To decode a BIP21 URI pass in a valid URI.

let bip21 =
  'bitcoincash:qrdsfshx7yzfjl9sfj2khuja5crcu4vaxqrt2qkz5s?amount=1&label=%23BCHForEveryone'
BITBOX.BitcoinCash.decodeBIP21(bip21)
// { address: 'qrdsfshx7yzfjl9sfj2khuja5crcu4vaxqrt2qkz5s', options: { amount: 1, label: '#BCHForEveryone' } }

Error handling

decodeBIP21 won’t accept incorrectly encoded BIP21 URIs

let bip21 =
  'qrdsfshx7yzfjl9sfj2khuja5crcu4vaxqrt2qkz5s?amount=1&label=%23BCHForEveryone'
BITBOX.BitcoinCash.decodeBIP21(bip21)
// Error: Invalid BIP21 URI: qrdsfshx7yzfjl9sfj2khuja5crcu4vaxqrt2qkz5s?amount=1&label=%23BCHForEveryone

Summary

BIP21 URIs are an extremely popular way to share payment requests. Now w/ encodeBIP21 and decodeBIP21 your app can create and process them.

More info

Find out more info about encodeBIP21

Find out more info about decodeBIP21

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