為什麼在 regtest 模式下會有 op-return 輸出？

這是來自的輸出getrawtransaction：

{
 "txid": "a2b9e3aa4adeb68a9b8b8b0bbc8d4890585cd711e89cda83e7f236397fac6218",
 "hash": "6d96c04d49eefe3eab4934188841ef3592c818bf789517b90b1f71ff75a14c26",
 "version": 2,
 "size": 183,
 "vsize": 156,
 "locktime": 0,
 "vin": [
   {
     "coinbase": "02b0010101",
     "sequence": 4294967295
   }
 ],
 "vout": [
   {
     "value": 12.50000000,
     "n": 0,
     "scriptPubKey": {
   "asm": "03d81b3d2ac76e322dcb2e713cb8fdeaf68cb83406c0e4d28dcd10a880ef172a6a OP_CHECKSIG",
   "hex": "2103d81b3d2ac76e322dcb2e713cb8fdeaf68cb83406c0e4d28dcd10a880ef172a6aac",
   "reqSigs": 1,
   "type": "pubkey",
   "addresses": [
     "mwzWcEU4kBkJPSTgB8LSBfvyaEjdXmyGh7"
   ]
     }
   }, 
   {
     "value": 0.00000000,
     "n": 1,
     "scriptPubKey": {
   "asm": "OP_RETURN aa21a9ede2f61c3f71d1defd3fa999dfa36953755c690689799962b48bebd836974e8cf9",
   "hex": "6a24aa21a9ede2f61c3f71d1defd3fa999dfa36953755c690689799962b48bebd836974e8cf9",
   "type": "nulldata"
     }
   }
 ],
 "hex": "020000000001010000000000000000000000000000000000000000000000000000000000000000ffffffff0502b0010101ffffffff02807c814a00000000232103d81b3d2ac76e322dcb2e713cb8fdeaf68cb83406c0e4d28dcd10a880ef172a6aac0000000000000000266a24aa21a9ede2f61c3f71d1defd3fa999dfa36953755c690689799962b48bebd836974e8cf90120000000000000000000000000000000000000000000000000000000000000000000000000",
 "blockhash": "4742b345fb92ce66f5fccaa880ebef29ebe44d8649114ddb06c4f7177047a717",
 "confirmations": 1,
 "time": 1512718207,
 "blocktime": 1512718207
}

我對這一點很感興趣：

{
 "value": 0.00000000,
 "n": 1,
 "scriptPubKey": {
   "asm": "OP_RETURN aa21a9ede2f61c3f71d1defd3fa999dfa36953755c690689799962b48bebd836974e8cf9",
   "hex": "6a24aa21a9ede2f61c3f71d1defd3fa999dfa36953755c690689799962b48bebd836974e8cf9",
   "type": "nulldata"
 }
}

誰創造了它？（我正在使用regtest模式）

你做到了，大概。

您顯示的交易是 coinbase；這是礦工添加的特殊交易。OP_RETURN 輸出是 SegWit 塊送出。它是所有交易的 wtxid（包括見證人的 txid）的 Merkle 根，從而確保區塊送出給所有見證人。

在 regtest 模式下執行時，您可能直接或間接地從一個稱為generateRPC 呼叫的腳本中生成一個新塊。如果區塊中有任何 SegWit 交易，則承諾是強制性的（否則是可選的）。

引用自：https://bitcoin.stackexchange.com/questions/64588