What this validator actually checks
A Bitcoin address is not just a string of characters: every format in use today carries a built-in checksum, so most typing mistakes make the address mathematically impossible rather than quietly wrong. This tool runs the same checks a wallet performs before it lets you send. It decodes the address, recomputes the checksum from scratch and confirms the structure matches a known address type, all in your browser, with nothing transmitted anywhere.
Addresses starting with 1 or 3 use Base58Check encoding. A leading 1 means P2PKH (pay to public key hash), the original format from 2009; a leading 3 means P2SH (pay to script hash), often multisig or wrapped SegWit. Both decode to exactly 25 bytes: a version byte, a 20 byte hash and a 4 byte checksum produced by hashing the first 21 bytes twice with SHA-256. Addresses starting bc1q are native SegWit, encoded with bech32 as defined in BIP-173, and bc1p means Taproot, which BIP-350 moved to the slightly different bech32m checksum. Testnet equivalents (prefixes m, n, 2 and tb1) are recognised and labelled too.
Try it with verified examples
Paste any of these into the tool above and you will see the same verdicts, worked out live from the raw maths rather than from a lookup table.
Why the checksum catches typos
Legacy addresses end with a 4 byte checksum, which is 32 bits, so a random corruption has roughly a 1 in 2^32 chance of slipping through. That is about 1 in 4.3 billion, which is why wallets flatly refuse mistyped addresses instead of sending coins into the void. Base58 helps before the maths even starts: the alphabet deliberately excludes the digit 0, capital O, capital I and lower case l, the four characters people confuse most often.
The bech32 format used by SegWit and Taproot goes further. Its checksum is a BCH code designed so that any error affecting up to four characters is guaranteed to be detected, and anything larger slips through with odds below one in a billion. It is also single case, which removes a whole class of transcription errors and makes QR codes smaller. The 2021 bech32m revision fixed a subtle weakness in the original design, which is why a Taproot address encoded with the old bech32 constant is rejected as invalid here, exactly as modern wallets reject it.
What a valid result does not mean
A passing checksum proves the characters were transcribed correctly. It does not prove the address belongs to the person you think it does, and it cannot, because this tool never touches the blockchain. Clipboard malware exists that swaps a copied address for an attacker's perfectly valid one, so compare the first and last few characters against the source before sending, and consider a small test transaction for large amounts. Bitcoin transactions cannot be reversed by anyone.
Never type a seed phrase or private key into any website, including this one. Addresses are public by design and safe to check anywhere; seed phrases are the keys to everything and belong only in your wallet. This page is technical guidance, not financial advice, and UK regulators class cryptoassets as high risk with little consumer protection, as the FCA's cryptoassets guidance explains.
Frequently asked questions
Is my address sent anywhere when I check it?
No. The validation maths runs entirely in your browser with JavaScript. Nothing is transmitted, logged or stored, and the tool never looks anything up on the blockchain. Once the page has loaded it works with no connection at all.
Does this tool show the balance of an address?
No. It checks structure and checksum only, which proves the address is well formed and free of typing errors. It does not query the blockchain, so it cannot tell you whether an address holds funds or has ever been used.
What do the different address types mean?
Addresses starting with 1 are legacy P2PKH, a leading 3 means P2SH (often multisig or wrapped SegWit), bc1q is native SegWit (P2WPKH or P2WSH) and bc1p is Taproot. All are spendable; the newer formats generally mean lower transaction fees.
Can a valid address still be the wrong address?
Yes. A passing checksum only proves the characters have not been mistyped. Malware that swaps addresses in your clipboard produces a different but perfectly valid address, so always compare the first and last few characters against the source before sending anything.
Should I ever type my seed phrase into a website to check it?
Never. No legitimate website, wallet support team or airdrop needs your seed phrase or private key, and anyone who asks for one is trying to steal your funds. This tool accepts public addresses only, which are safe to share.