who know some javascript library for decoding optimized Micheline representation of an address value?

011cd5f135e80fd8ebb6e43335b24ca6116edeba6900 => KT1BDEn6wobs7tDReKkGheXAhoq278TGaNn5

2 Answers 2


Optimized addresses are 22 bytes, which follows the following format:

  • The first byte is a tag, either 00 for implicit (tz) or 01 for originated (KT)

If the first byte is 00 and we are working with an implicit (tz) address, then:

  • The second byte describes the curve and therefore the prefix. This is either 00 (ed25519/tz1), 01 (secp256k1/tz2) or 02 (p256/tz3)
  • The remaining 20 bytes is the address

If the first byte is 01 and we are working with an originated (KT) address, then:

  • The next 20 bytes are the address
  • The last byte is a 00 buffer (to pad the length to 22 bytes)

To convert the optimized form to an address, you can use eztz and do something like this:

function getAddressFromOptimized(hex){
  var address, prefix;
  if (hex.substring(0,2) == "00") {
    if (hex.substring(2,4) == "00") prefix = eztz.prefix.tz1;
    if (hex.substring(2,4) == "01") prefix = eztz.prefix.tz2;
    if (hex.substring(2,4) == "02") prefix = eztz.prefix.tz3;
    address = hex.substring(4,44);
  } else if (hex.substring(0,2) == "01"){
    prefix = eztz.prefix.KT;
    address = hex.substring(2,42);
  return eztz.utility.b58cencode(eztz.utility.hex2buf(address), prefix);

The format is documented here: http://tezos.gitlab.io/mainnet/api/p2p.html#contract-id-22-bytes-8-bit-tag


I believe you should be able to make use of Stephen Andrews eztz library to access various tools from a js environment

I would speculate the function is this one where you use the KT prefix

  b58cencode: function (payload, prefix) {
    const n = new Uint8Array(prefix.length + payload.length);
    n.set(payload, prefix.length);
    return library.bs58check.encode(new Buffer(n, 'hex'));
  • 1
    Ezy thanks for answer, but i try eztz.utility.b58cencode('011cd5f135e80fd8ebb6e43335b24ca6116edeba6900',eztz.prefix.KT) and this will return me "8RYhTWyrcLNgHVTCLfb3KP9TzGRZzttWK7CUJyYNLSD9xjpwC918e3BfpYBpwPBTy5UCi" not "KT1BDEn6wobs7tDReKkGheXAhoq278TGaNn5" Feb 2, 2019 at 22:48
  • 1
    @МихаилМагомедов yea sorry there were extra steps involved prior to calling that function as stephen showed!
    – Ezy
    Feb 3, 2019 at 3:26

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