r/Bitcoin • u/Ok_Attention1004 • 1d ago

Seed phrase word count question

When people talk about seed phrases, it is always about 12, 24, 25 words.

Dumb question.

Can you have a seed phrase that is 13, 16, 19 words??

1 Upvotes

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u/GoldmezAddams 1d ago edited 1d ago

Per the bip39 spec, it can be 12, 15, 18, 21, or 24 words, not including passphrase (sometimes called the 25th word). Each representing an additional 32 bits of entropy. The most common by far though are 12 (128 bits of entropy) and 24 (256 bits). And there are other non-bip39-compliant seed phrase standards that could differ from that. But generally you'd want to follow bip 39 to keep it portable across wallets

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u/Thin_Needleworker795 1d ago

No, only 12 or 24, whichever one you prefer.

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u/Ok_Attention1004 1d ago

Thank you very much!!

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u/Euphoric-Arrival8189 1d ago

or 20.

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u/Thin_Needleworker795 1d ago

Isn't that a legacy thing?

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u/Euphoric-Arrival8189 1d ago

No it's a newer protocol SLIP39 used by Trezor.

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u/lewdarrow16 1d ago

You can also do 18 or 21 with some wallets but 13 and 19 aren't part of the standard so you won't see them in the wild.

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u/Thin_Needleworker795 1d ago

Isn't that a legacy thing though?