Definition
P2PKH (Pay to Public Key Hash) is Bitcoin's original standard address type, the default wallets used from 2009 until SegWit arrived in 2017. A P2PKH address is the Base58Check encoding of a 20-byte HASH160 of a public key, carrying a 0x00 version byte that makes every mainnet P2PKH address begin with the numeral 1. Because it predates Segregated Witness, it is commonly called a legacy address.
How the lock works
The output's locking script (scriptPubKey) is OP_DUP OP_HASH160 <pubKeyHash> OP_EQUALVERIFY OP_CHECKSIG. To spend, the owner supplies a signature and the full public key in the input's scriptSig. The script duplicates and hashes the supplied key, checks it against the committed hash, then verifies the signature. Revealing the public key only at spend time was an early privacy and safety measure baked in by Satoshi.
Why it still matters
Legacy outputs are heavier than witness outputs because the unlocking data lives in the scriptSig rather than a discounted witness field, so spending from a P2PKH address costs more in fees. Many older wallets, exchanges, and hardware devices still generate and accept type-1 addresses, so they remain in active use. Self-sovereign operators auditing UTXOs should recognize the prefix to estimate spend costs and plan consolidation.
For the witness-discounted successor see P2WPKH (Native SegWit), and for the encoding scheme legacy addresses share see the broader context of SegWit.
In Simple Terms
P2PKH (Pay to Public Key Hash) is Bitcoin’s original standard address type, the default wallets used from 2009 until SegWit arrived in 2017. A P2PKH…