BTC Notes

Getting unspent outputs of a public address

curl https://blockchain.info/unspent?active={{address}}
curl https://blockchain.info/unspent?active=1Cdid9KFAaatwczBwBttQcwXYCpvK8h7FK

{
  "notice": "",
  "unspent_outputs": [
    {
      "tx_hash_big_endian": "ce3454376a468f3fa7f241355724dd340fde63b9e51d7da3c3197a97691d0534",
      "tx_hash": "34051d69977a19c3a37d1de5b963de0f34dd24573541f2a73f8f466a375434ce",
      "tx_output_n": 1,
      "script": "76a9147f9b1a7fb68d60c536c2fd8aeaa53a8f3cc025a888ac",
      "value": 9978,
      "value_hex": "26fa",
      "confirmations": 233403,
      "tx_index": 1830290334084931
    },
    {
      "tx_hash_big_endian": "b45a9cb4a1061b7c48752757c44c28575051366483c54c9934036130c4752289",
      "tx_hash": "892275c430610334994cc5836436515057284cc4572775487c1b06a1b49c5ab4",
      "tx_output_n": 1,
      "script": "76a9147f9b1a7fb68d60c536c2fd8aeaa53a8f3cc025a888ac",
      "value": 6236,
      "value_hex": "185c",
      "confirmations": 322484,
      "tx_index": 4824995125922848
    },
    {
      "tx_hash_big_endian": "ee5f17e9d821ca5d3ad7b221ba48820e8301a79e57a8660c7ac1b8db2b5c34bd",
      "tx_hash": "bd345c2bdbb8c17a0c66a8579ea701830e8248ba21b2d73a5dca21d8e9175fee",
      "tx_output_n": 1,
      "script": "76a9147f9b1a7fb68d60c536c2fd8aeaa53a8f3cc025a888ac",
      "value": 3020,
      "value_hex": "0bcc",
      "confirmations": 354516,
      "tx_index": 6657042634471192
    }
    ]
}

UTXO Response Parameters

Each unspent transaction output (UTXO) returned from the API contains several important fields:

• tx_hash_big_endian:

  • Transaction hash in "big-endian" format (most significant byte first).
  • A 64-character hexadecimal string uniquely identifying the transaction.

• tx_hash:

  • Transaction hash in "little-endian" format (least significant byte first), commonly used in Bitcoin explorers.
  • This is the reverse of tx_hash_big_endian.

• tx_output_n:

  • Output index number within the transaction.
  • Each transaction can contain multiple outputs; this number identifies which output this UTXO represents, starting from 0.

• script:

  • The scriptPubKey for the output, in hexadecimal format.
  • Specifies the conditions needed to spend this output, typically containing a locking script.
  • Example script: 76a9147f9b1a7fb68d60c536c2fd8aeaa53a8f3cc025a888ac, which represents a Pay-to-PubKey-Hash (P2PKH) script.

• value:

  • The amount of Bitcoin available in this output, in satoshis (1 BTC = 100,000,000 satoshis).

• value_hex:

  • The value in hexadecimal format, representing the same amount as value but in hexadecimal.

• confirmations:

  • The number of confirmations this output has received.
  • A higher number indicates greater security and inclusion in multiple blocks.

• tx_index:

  • A unique identifier for this transaction output in the blockchain.info database.
  • Useful for tracking within their system, though it may not be required in most Bitcoin applications.