Is your Bitcoin address quantum-exposed?
Paste an address. We'll tell you whether its public key is visible on the blockchain, what that means, and whether you need to do anything. Usually you don't.
Check an address
Find it in your wallet's receive screen or transaction history. The type check runs in your browser as soon as you paste.
Checking history is optional. It sends this one address to mempool.space, which logs your IP address with the request for 10 days. If mempool.space is unavailable, it goes to blockstream.info instead, which also logs IP addresses. Use a VPN or Tor if that matters to you. Everything else runs in your browser, and 21VOX never sees the address.
Three ways a public key ends up on-chain
Spending, then reusing
Every time an address signs a transaction, its public key is published. Coins left at that address afterward sit behind a visible key.
Taproot addresses
Addresses starting with bc1p carry a public key from the moment they receive coins. That is part of how Taproot works, not a bug.
The earliest coins
Bitcoin's first years used pay-to-public-key outputs, including coins attributed to Satoshi. They have no address to paste, so this tool doesn't check them.
| Starts with | Address type | Public key before first spend |
|---|---|---|
| 1 | Legacy (P2PKH) | Hidden behind a hash |
| 3 | Script hash (P2SH), incl. wrapped SegWit and older multisig | Hidden behind a hash |
| bc1q | Native SegWit (P2WPKH, P2WSH) | Hidden behind a hash |
| bc1p | Taproot (P2TR) | Visible on-chain |
Questions
Should I move my coins because of quantum computers?
Not in a hurry. No computer today can derive a private key from a public key, and rushed migrations cause real losses. Using a fresh address for each payment is enough for now.
Why don't you ask for my seed phrase or xpub?
Because this tool doesn't need them, and nothing legitimate does. Anyone asking for a seed phrase to "check" or "protect" your coins is trying to steal them.
What does the on-chain check send?
Only the address you typed, sent from your browser to the mempool.space public API to look up its transaction history. mempool.space logs your IP address with the request for 10 days, per its privacy policy. If mempool.space is unavailable, the same lookup goes to blockstream.info instead, which also logs IP addresses. The check is off by default, and 21VOX never receives or stores the address.
Why one address at a time?
Looking up several addresses from the same connection lets the explorer link them to each other as one person's wallet. Checking one at a time means you decide, each time, what gets sent. If you check more than one, consider a VPN or Tor.
My coins are on an exchange. Does this apply?
No. The exchange holds the keys and manages its own addresses, so a deposit address tells you nothing about your coins. This check is for addresses in a wallet you control.
Is anything being done about this?
Yes, slowly and in public. BIP-360, merged into the BIP repository in February 2026, proposes an output type without Taproot's key exposure as groundwork for future quantum-resistant signatures. It had not been activated as of October 2026.
Moving coins changes your family's plan.
Whenever your coins move, the instructions your family would rely on change too. Bitcoin Legacy, the inheritance planner we're building, turns them into three printable documents. In development.
Join the Legacy waitlist