What is Polyseed? The 16-word Monero seed explained
Feather shows a 16-word recovery phrase by default — that is Polyseed. Here is what it is, why it is shorter than the classic 25-word Monero seed, and how the two formats relate.
The short version
Polyseed is a 16-word mnemonic format for Monero wallet seeds. It encodes the same 256-bit secret as the classic 25-word Monero seed, but packs it into fewer, more distinct words — and adds two small fields the old format never had: a birthday (when the wallet was created) and a feature word (what the seed is for). Feather Wallet generates a Polyseed by default, which is why you see 16 words instead of 25.
Why 16 words instead of 25?
The classic Monero phrase stores 32 bytes of key material as 24 words of 32-bit chunks plus one checksum word. Polyseed takes a different route: it encodes 150 secret bits over 15 words and keeps the 16th word for a checksum, using a 2048-word list (the familiar BIP39 English list, alphabetically ordered). Fewer words to write down, fewer chances to make a transcription mistake, and a stronger checksum that catches errors more reliably.
| Property | Polyseed | Legacy Monero seed |
|---|---|---|
| Word count | 16 | 25 |
| Wordlist | 2048 words | 1626 words |
| Checksum | Dedicated word + birthday/features | 1 checksum word (24 mod) |
| Creation date stored | Yes (birthday) | No |
| Wallet support | Feather, Monero CLI/GUI (recent) | Every Monero wallet |
What is the “birthday” for?
When you restore a legacy seed, the wallet has no idea when the wallet was created, so it must scan the blockchain from a conservative starting point — potentially years of blocks. Polyseed stores the creation month, so a restore can start scanning near the right block height and synchronize dramatically faster.
Can you convert Polyseed to 25 words?
Yes, in one direction at a time and on the same machine: any wallet that can derive the keys can re-encode them. Feather shows a “Show 25 word seed” toggle next to the generated 16-word phrase — flipping it displays the same wallet as a legacy 25-word phrase, and the derived address does not change. That is the comfortable way to migrate: keep both forms on paper if some older tool only accepts 25 words.
Is 16 words less secure than 25?
No. Security comes from the 256-bit key behind the words, not from how many words are printed. Polyseed's 150-bit payload plus key derivation through PBKDF2 (10,000 iterations) produces the same strength class as the legacy seed. A brute-force attack on either format is infeasible; the practical risk is always human — a photographed backup, a clipboard stealer or a phrase typed into a fake site.
Where Polyseed is supported
Polyseed was designed by tevador as a compact, modern replacement for the Monero mnemonic and is supported by Feather Wallet (desktop and the browser wallet) and by recent versions of the official Monero CLI/GUI. If you plan to move a wallet into an older tool, check that it accepts 16-word phrases — otherwise use the 25-word view.
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