Guess which chain an address belongs to from its shape and encoding, without requiring the caller to know it up front. Returns the chain, format and address type, or nulls when nothing matches.

Apply the EIP-55 mixed-case checksum to an Ethereum address, regardless of its input casing. Returns the checksummed address and whether it differed from the input. Non-hex input is rejected before payment.

Normalise an address to its canonical form — Ethereum to its EIP-55 checksummed form, bech32 Bitcoin to lowercase (base58check is left untouched as it is case-sensitive). An address that is not a valid address of a known chain is rejected before payment.

Validate a blockchain address. Supply `chain` to check against a specific chain, or omit it to auto-detect. Ethereum addresses report their EIP-55 checksum state; Bitcoin covers base58check (P2PKH/P2SH) and bech32/bech32m segwit (P2WPKH/P2WSH/P2TR). A well-formed but invalid address returns `valid:false` — not an error.