BIP39 Mnemonic Generator
Generate and verify BIP39 recovery phrases with the official 2048-word list and SHA-256 checksum. Free online tool, browser-based, no signup.
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Frequently asked questions
- Should I use this for a real wallet?
- For anything you cannot afford to lose, no. The phrase is generated correctly, but a browser cannot defend against extensions, clipboard readers, or a compromised device. Generate real seeds on a hardware wallet.
- Is the phrase generated securely?
- Entropy comes from crypto.getRandomValues, the browser CSPRNG, using the official 2048-word BIP39 English list and a SHA-256 checksum. Output matches the standard BIP39 test vectors.
- What is BIP39?
- Bitcoin Improvement Proposal 39 defines how a wallet seed is encoded as a mnemonic phrase: random entropy plus a checksum, split into 11-bit groups that each map to one word in a fixed 2048-word list.
- Word count options?
- 12, 15, 18, 21, 24 - corresponding to 128, 160, 192, 224, 256 bits of entropy plus a checksum of one bit per 32 bits of entropy.
- Why does my phrase fail the checksum?
- The last word encodes a checksum over the preceding entropy, so a single mistyped or reordered word makes the phrase invalid. The checker names any word that is not in the BIP39 list.
- Does anything leave my device?
- No. Generation and validation run in your browser; no phrase is transmitted, logged, or stored.