Address Generation & Validation
Bitcoin addresses are human-readable encodings of output scripts. Understanding how to generate, validate, and work with different address types is fundamental to Bitcoin development.
Address Types Overview
Legacy Addresses (P2PKH)
Format: Starts with 1 (mainnet) or m/n (testnet)
1BvBMSEYstWetqTFn5Au4m4GFg7xJaNVN2
Script: Pay-to-Public-Key-Hash
OP_DUP OP_HASH160 <pubkey_hash> OP_EQUALVERIFY OP_CHECKSIG
Script Hash Addresses (P2SH)
Format: Starts with 3 (mainnet) or 2 (testnet)
3J98t1WpEZ73CNmQviecrnyiWrnqRhWNLy
Script: Pay-to-Script-Hash (can contain any script)
OP_HASH160 <script_hash> OP_EQUAL
Native SegWit (P2WPKH)
Format: Starts with bc1q (mainnet) or tb1q (testnet)
bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq
Script: Pay-to-Witness-Public-Key-Hash
OP_0 <20-byte-pubkey-hash>
Native SegWit Script (P2WSH)
Format: Starts with bc1q but longer (mainnet)
bc1qrp33g0q5c5txsp9arysrx4k6zdkfs4nce4xj0gdcccefvpysxf3qccfmv3
Script: Pay-to-Witness-Script-Hash
OP_0 <32-byte-script-hash>
Taproot (P2TR)
Format: Starts with bc1p (mainnet) or tb1p (testnet)
bc1p5d7rjq7g6rdk2yhzks9smlaqtedr4dekq08ge8ztwac72sfr9rusxg3297
Script: Pay-to-Taproot
OP_1 <32-byte-x-only-pubkey>
Address Comparison
| Type | Prefix | Size | Encoding | Fee Efficiency |
|---|---|---|---|---|
| P2PKH | 1 | 25 bytes | Base58Check | Lowest |
| P2SH | 3 | 23 bytes | Base58Check | Low |
| P2WPKH | bc1q | 22 bytes | Bech32 | High |
| P2WSH | bc1q | 34 bytes | Bech32 | Medium |
| P2TR | bc1p | 34 bytes | Bech32m | Highest |
Generating Addresses
From Public Key to P2WPKH (Native SegWit)
Validating Addresses
Bech32 Encoding Details
Bech32 vs Bech32m
Bech32 (BIP-173):
- Used for SegWit v0 (P2WPKH, P2WSH)
- Checksum constant: 1
Bech32m (BIP-350):
- Used for SegWit v1+ (Taproot)
- Checksum constant: 0x2bc830a3
Why Bech32m?
Bech32 had a weakness where certain error patterns could go undetected. Bech32m fixes this for future witness versions.
From Script to Address
Address Derivation Paths
BIP Standards
| BIP | Path | Address Type | Example |
|---|---|---|---|
| BIP44 | m/44'/0'/0' | P2PKH | 1... |
| BIP49 | m/49'/0'/0' | P2SH-P2WPKH | 3... |
| BIP84 | m/84'/0'/0' | P2WPKH | bc1q... |
| BIP86 | m/86'/0'/0' | P2TR | bc1p... |
Deriving Addresses from Seed
Multi-Signature Addresses
Creating 2-of-3 Multisig
Common Mistakes
Address Validation Pitfalls
- BAD: Only checking prefix (
address.startsWith('bc1')) - GOOD: Full validation with checksum verification using library functions
Network Mismatch
Always use consistent network parameters. Never mix mainnet keys with testnet addresses.
Checksum Errors
Always validate checksums before using an address - all libraries provide validation functions.
Best Practices
Address Generation
- Use Established Libraries: Don't implement encoding yourself
- Validate After Generation: Always verify the generated address
- Use Appropriate Types: Prefer SegWit/Taproot for lower fees
- Test on Testnet: Verify address generation works correctly
Address Handling
- Case Sensitivity: Bech32 is case-insensitive, Base58 is case-sensitive
- Display Formatting: Consider QR codes for long addresses
- Copy Protection: Use checksums to detect copy errors
- Network Verification: Always verify mainnet vs testnet
Security
- Never Reuse Addresses: Generate new addresses for each transaction
- Verify Derivation Paths: Ensure consistent paths across wallet imports
- Backup Seeds: Addresses can be regenerated from seeds
Summary
Understanding Bitcoin addresses requires knowledge of:
- Encoding Schemes: Base58Check, Bech32, Bech32m
- Script Types: P2PKH, P2SH, P2WPKH, P2WSH, P2TR
- Derivation: BIP32/39/44/49/84/86 standards
- Validation: Checksum verification and format checking
Modern applications should default to Bech32m (Taproot) addresses for the best fee efficiency and privacy features.
Related Topics
- Key Management - Managing private and public keys
- Address Types - Detailed address type comparison
- HD Wallets - Derivation paths and wallet structure
- Transaction Construction - Using addresses in transactions