BIP39 Mnemonic Generator
Generate cryptographically secure mnemonic seed phrases with 12, 18, or 24 words for HD wallets.
Mnemonic Generator
Security Warning
This mnemonic phrase is generated locally in your browser using cryptographically secure random values. Save it in a secure offline location. Never share your seed phrase with anyone. Anyone with access to this phrase can control your wallet.
- Select word count — Choose 12, 18, or 24 words. More words = higher security.
- Generate — Click the Generate button. A new cryptographically secure mnemonic phrase is created using your browser's Crypto API.
- Copy and save — Copy the phrase and store it securely offline. The phrase is your wallet's master seed.
- Verify — Always verify your backup by restoring the phrase in your wallet before sending funds.
All generation is performed 100% client-side in your browser using crypto.getRandomValues() for cryptographically secure entropy. No data is sent to any server.
What Is BIP39?
BIP39 (Bitcoin Improvement Proposal 39) defines the standard for generating mnemonic seed phrases used in hierarchical deterministic (HD) wallets. A BIP39 mnemonic is a sequence of words chosen from a fixed wordlist of 2048 words that encodes a random entropy value used to derive all wallet keys.
The generation process works as follows: random entropy (128, 192, or 256 bits) is generated, a checksum derived from SHA-256 is appended, and the combined bit string is split into 11-bit segments. Each 11-bit value (0-2047) maps to a word in the BIP39 English wordlist, producing the mnemonic phrase.
The mnemonic can optionally be combined with a passphrase (BIP39 passphrase) to generate the wallet seed, adding an extra layer of security. The standard is supported by virtually all cryptocurrency wallets, including Bitcoin Core, Ledger, Trezor, MetaMask, Trust Wallet, and many others.
BIP39 Word Count Comparison
| Words | Entropy | Checksum | Security Level | Recommended Use |
|---|---|---|---|---|
| 12 | 128 bits | 4 bits | Standard | Most wallets, good balance of security and convenience |
| 18 | 192 bits | 6 bits | High | High-value wallets, extra security margin |
| 24 | 256 bits | 8 bits | Maximum | Cold storage, institutional, maximum security |
What is a BIP39 mnemonic seed phrase?
A BIP39 mnemonic seed phrase is a human-readable representation of the entropy used to generate all keys in a hierarchical deterministic (HD) wallet. It typically consists of 12, 18, or 24 words from a standard wordlist of 2048 words.
Which word count should I choose?
12 words (128-bit) is sufficient for most users and is the most commonly used standard. 24 words (256-bit) provides maximum security and is recommended for cold storage and large holdings. 18 words offers a middle ground.
Are these phrases compatible with my wallet?
Yes. BIP39 is an industry standard supported by virtually all cryptocurrency wallets including Bitcoin Core, Ledger, Trezor, MetaMask, Trust Wallet, Electrum, Exodus, and hundreds more.
How is the entropy generated?
This tool uses the browser's crypto.getRandomValues() API, which provides cryptographically secure random values sourced from the operating system's entropy pool. This is the same source used by most wallet software.
Can I add a passphrase (BIP39 passphrase)?
This tool generates the mnemonic phrase only. You can add a BIP39 passphrase in your wallet software when restoring the wallet. The passphrase combined with the mnemonic produces the final wallet seed, adding an extra layer of protection.
How should I store my seed phrase?
Store it offline on paper or metal (steel/cryptosteel) in a fireproof safe. Never store it digitally (screenshots, cloud, email, text files). Never enter it into websites or apps that you don't fully trust. Consider splitting it using a BIP39 passphrase for additional security.