bitcoin addresses that begin with the digit “1” are the original, legacy address format used on the bitcoin network and implement the Pay-to-Public-Key-Hash (P2PKH) script type. These addresses were the default in bitcoin’s early years and remain valid and widely accepted by wallets and services, but they are considered legacy compared with newer address standards. Modern wallets increasingly use SegWit-based formats (for example,P2WPKH and bech32 addresses) and other BIP-defined schemes to improve efficiency,lower fees,and reduce transaction malleability [[3]](), [[2]](). This article explains what makes “1”-prefixed P2PKH addresses distinct, how they work at a technical level, the practical implications for compatibility, fees, and privacy, and when users and services should consider migrating to newer address types.
Understanding bitcoin addresses that start with one and Pay to Public Key Hash fundamentals
Addresses that begin with the digit “1” are the original bitcoin address form known as Pay to Public Key Hash (P2PKH). They are encoded with Base58Check and use a version byte of 0x00, which is why the human-readable portrayal starts with “1”.The spending script behind these addresses follows the classic pattern: OP_DUP OP_HASH160 , where the public key hash is 20 bytes (160 bits). this legacy format is widely recognized and remains valid on the bitcoin network, but it does not provide some of the size and fee advantages introduced by later address types.
- Script type: P2PKH (legacy)
- Address prefix: Base58Check leading “1”
- PubKey hash length: 20 bytes (160 bits)
- Compatibility: Universally supported by older and many modern wallets, though newer wallets may prefer SegWit formats
- Tradeoffs: Larger transaction size and higher fees compared with SegWit-based outputs
Hierarchical Deterministic (HD) wallets and modern wallet standards were designed to manage multiple address formats (legacy and newer types) in a structured way so users can derive and organize addresses reliably across devices and applications . that compatibility layer explains why many wallet implementations still generate and accept “1”-prefixed addresses even as the ecosystem shifts toward SegWit and bech32 styles.
| Format | Prefix | Typical script |
|---|---|---|
| P2PKH | 1… | OP_DUP OP_HASH160 |
| P2SH | 3… | OP_HASH160 |