Closed vs open: the two states that matter
Updated September 2026
Every page on this site uses two words. Closed means the public key is still behind a hash. Open means that key is sitting on the chain for anyone to read. The checker reports those two states. This page is the legend.
Closed
A P2PKH address (starts with 1), a P2SH address (3), or a SegWit v0 address (bc1q) is built from a hash of a public key. Until that address spends, the chain shows the hash and nothing else. Reversing a hash is a different problem from the elliptic-curve problem a large quantum computer would be good at. The box stays shut.
Closed does not mean unused forever. It means unused as an input. Receiving coins does not open a hash-based box. Spending does. Sending a second payment from the same address is opening it again after the first observation already happened.
Open
Three common ways a box is already open:
- A hash-based address that has spent at least once. The signature published the public key. That publication is permanent.
- Any Taproot address (bc1p). The address itself commits to the key. Receipt is observation. See why Taproot is open on arrival.
- Older pay-to-pubkey outputs, including a large share of very early coins. There was never a hash in front of the key.
Open is the tier that future migration proposals talk about. Roughly 5.4 million BTC sits there, mostly from ordinary spending over fifteen years, not from carelessness.
The table
| What you are looking at | State | When the key became public |
|---|---|---|
| 1 / 3 / bc1q, never spent | Closed | Not yet |
| 1 / 3 / bc1q, spent at least once | Open | First spend |
| bc1p Taproot | Open | On receipt |
| P2PK and similar early outputs | Open | On creation |
What this is not
It is not superposition. The public key is a fixed number the whole time. We simply cannot read it from a hash with anything that exists. Why the cat says where the metaphor must stop. It is also not an emergency. Bitcoin is safe from quantum computers today. Closed versus open is the fact you can check before anyone asks you to panic.
Quick answers
- What is a closed Bitcoin address?
- A hash-based address (1, 3, or bc1q) that has never spent. Only a hash of the public key is on-chain.
- What is an open Bitcoin address?
- Any address whose public key is already visible: a spent hash-based address, any Taproot address, or older pay-to-pubkey outputs.
- Does open mean the coins can be stolen today?
- No. Breaking secp256k1 still requires a quantum computer that does not exist. Open is a published fact, not an alarm.