Files · Key formats
Keys starting with 5, K or L: what each format means
If you found a long string of letters and numbers and don’t know what it is, the first character tells you almost everything. It is the fastest way to know what you are holding before touching anything.
The quick table
| Starts with | What it is | Approximate length |
|---|---|---|
| 5 | Bitcoin private key, old format | 51 characters |
| K or L | Bitcoin private key, compressed format | 52 characters |
| 6P | Password-protected private key | 58 characters |
| xprv | Master key: controls an entire wallet | 111 characters |
| xpub, ypub, zpub | Master public key: view only, cannot spend | 111 characters |
| 0x followed by 64 characters | Ethereum private key | 66 characters |
| 1, 3 or bc1 | An address, not a key | 26 to 62 |
The two things to know
First: the rows above, except xpub and the last one, are money. Anyone who reads that string can empty the wallet in a minute. They are not photographed, not pasted into websites and not sent by chat, ever.
Second: the two that are harmless — the address and the ones starting with xpub, ypub or zpub — are exactly the ones used to check for a balance and to prove the wallet is yours. You can share them without fear and they are precisely what is asked for when assessing a case.
If what you have is a master key
A key starting with xprv is the equivalent of the recovery phrase: it controls the whole wallet, every account and every address. If you have it, you need neither the phrase nor the password: you can import it into a compatible wallet and recover everything. Treat it with the same care you would the phrase.
What those long keys actually mean is explained calmly in xprv, ypub, zpub: what those long keys are.