A private key controls one address. A seed phrase generates all your private keys — an effectively unlimited supply of them, across multiple coins, from twelve or twenty-four words.
That is the whole distinction, and nearly every practical question follows from it: which one to back up, why you never see your private keys in a modern wallet, and why importing a single key into a wallet behaves so strangely.
The chain of derivation
Everything descends from the phrase in one direction:
recovery phrase (12 or 24 words)
|
v key stretching
master seed (512 bits)
|
v BIP-32 tree
account keys -> child private keys (unlimited)
|
v one-way
public keys -> addresses
Each arrow is computable downward and infeasible upward. From the phrase you can regenerate every key you have ever had. From one private key you can derive its address. From an address you can derive nothing — which is why publishing an address is safe and publishing a key is catastrophic.
The derivation is also deterministic. The same phrase always produces the same keys in the same order, on any compatible wallet. That is what makes a phrase a backup: you are not storing keys, you are storing the recipe that recreates them.
Practical consequences
- Back up the phrase, not keys. The phrase covers every address you have and every address you will ever generate. Backing up individual private keys means re-backing-up each time you use a new address, which is exactly the failure mode that hierarchical wallets were invented to eliminate.
- A new receiving address needs no new backup. It is another leaf on a tree you already hold.
- One phrase covers many coins. Bitcoin and Ethereum sit on different branches of the same tree.
- Losing one private key does not lose the wallet — you can regenerate it from the phrase. Losing the phrase, with no other backup, loses everything.
Where you still meet raw private keys
Modern wallets hide them, but they surface in a few places:
- Paper wallets from the mid-2010s — a single keypair printed as text and QR. They predate hierarchical wallets and have no phrase.
- WIF strings, the Bitcoin encoding beginning with
5,KorL. - Ethereum keys, a 64-character hexadecimal string, often shown with a
0xprefix. - Exported keys from a wallet’s advanced settings, occasionally needed to move a single address elsewhere.
A raw private key is exactly as sensitive as a phrase, with none of the error-checking. A phrase has a checksum, so a mistyped word is usually rejected; mistype a hex key and you may silently produce a valid key to an unrelated empty wallet.
Why importing a single key behaves oddly
Import one private key into a wallet built around a phrase and it sits outside the tree. It is a guest, not a descendant.
The consequence catches people out: your recovery phrase does not back up an imported key. Restore that wallet from its phrase on a new device and the imported address will be missing, along with anything in it — because it was never derivable from the phrase in the first place.
If you have imported keys, either back each one up separately, or better, sweep them: send the funds to an address the wallet derives itself. After that the phrase genuinely covers everything, which is the state you want.
The extended public key, and a privacy trap
One more object worth knowing, because it is easy to leak: the extended public key (an xpub or similar). It lets software generate all your public addresses without any ability to spend — useful for watch-only wallets and accounting tools.
It cannot steal your money. It can destroy your privacy: anyone holding it can enumerate every address you will ever use and watch your entire balance and history, forever. Treat it as sensitive personal data even though it is not a key.
The short version
| Private key | Recovery phrase | |
|---|---|---|
| Controls | One address | Every address, all coins |
| Looks like | Hex or WIF string | 12 or 24 dictionary words |
| Typo protection | None | Checksum rejects most errors |
| Back this up? | Only if imported | Yes — this is the one |
If you take one thing: the phrase is the wallet. Guard it, store it properly, and never type it into a web page — not for a balance check, not for a migration, and not here.