BIP39 seed phrase generator

What a paper wallet actually is. A “paper wallet” is simply your recovery phrase kept on something physical instead of on a device. The words are the wallet: enter the same 12 or 24 words into any BIP39-compatible wallet and you recover the exact same accounts. This tool lays a freshly-made phrase onto a clean, printable Luck.fyi sheet — numbered slots, a date, a name, and a keep-secret warning — so a backup looks deliberate instead of being a scrap of paper you’ll lose.

Why we blur it, and why client-side matters. The sheet is hidden behind a blur the instant it’s drawn, because the quickest way to lose a phrase is to flash it on a stream, a screen-share, or in front of a window. Everything runs in your browser using crypto.getRandomValues and the native crypto.subtle SHA-256 — the same engine as the generator above — so the words never travel across the network. That genuinely makes the act of generating and viewing private.

A seed phrase — also called a recovery phrase or mnemonic — is a list of 12 or 24 ordinary words that represents the master key to a cryptocurrency wallet. From that single phrase, a wallet can mathematically derive every private key and address it will ever use. That's powerful and dangerous in equal measure: whoever holds the phrase controls the funds, with no bank, password reset, or customer service to fall back on.

Words are used instead of a long string of random characters for one simple reason: humans are far better at writing down, checking, and re-typing real words than hexadecimal. The standard that makes this work, used by almost every modern wallet, is BIP39.

BIP39 (Bitcoin Improvement Proposal 39) defines how random data becomes a memorable phrase. It specifies a fixed dictionary of exactly 2048 carefully chosen English words — each word distinct enough in its first four letters to avoid confusion. Because 2048 = 2¹¹, every word encodes exactly 11 bits of information.

The clever part is the checksum. BIP39 doesn't just slice your entropy into words — it appends a few bits derived from a SHA-256 hash of that entropy. Those extra bits become part of the final word, so if you mistype or mis-order words, a wallet can detect the error instead of silently loading the wrong (empty) wallet. A 12-word phrase = 128 bits of entropy + 4 checksum bits; a 24-word phrase = 256 bits + 8 checksum bits.

We follow the BIP39 spec exactly, in your browser:

1. Generate 128 or 256 bits of entropy from crypto.getRandomValues — your device's cryptographically-secure randomness, not the predictable Math.random().
2. Take a SHA-256 hash of that entropy (via the browser's native crypto.subtle) and append the first few bits as the checksum.
3. Split the combined bits into 11-bit groups, and map each group to a word in the official 2048-word list.

The result is a genuinely valid mnemonic that passes checksum verification in real wallets — generated locally, with nothing transmitted, logged, or stored. You can expand "technical details" on any phrase to see the raw entropy behind it.

This tool exists to demystify the most important — and most misunderstood — object in self-custody. It's ideal for learning how BIP39 works, experimenting with test wallets and development, and seeing real entropy turned into a valid phrase. It is not a substitute for a hardware wallet when real money is involved.

12 vs 24 words: a 12-word phrase carries 128 bits of entropy; a 24-word phrase carries 256 bits. Both are so far beyond any conceivable brute-force attack that neither will ever be guessed. The practical difference is margin: 24 words is the common choice for high-value, long-term, or institutional storage, while 12 words is perfectly strong for everyday use.

We built this tool to be private by design: every phrase is generated locally in your browser, and nothing is ever sent to a server, logged, or stored. But privacy is only half of safety. The single most important rule of self-custody is this: a recovery phrase that protects real funds should be created on a dedicated offline device — a hardware wallet — never on any website, ours included. Browsers can carry malware, extensions, and screen-capture risks no web page can rule out.

Standards-based. This generator implements the public BIP39 specification — the same 2048-word English list and checksum scheme used across the wallet ecosystem — so phrases are interoperable and verifiable, not a homegrown scheme.

Transparent. The entire process runs client-side and we show you the underlying entropy on request. We don't obscure how it works or ask for blind trust.

Independent & non-custodial. Luck.fyi is not a wallet, exchange, or custodian. We never hold keys or funds, and nothing here is financial advice. Our only goal is to help you understand and handle seed phrases safely.