BIP39 Mnemonic Generator

Generate BIP39 mnemonic seed phrases for cryptocurrency wallets in 12, 15, 18, 21, or 24 words.

BIP39 Mnemonic Generator tool

Loading...

Example

Input: Word Count 12 words (128 bits), then Generate Mnemonic

Result: Mnemonic Phrase (12 words): 12 numbered words from the 2,048-word BIP39 English list, different on every run

128 random bits plus a 4-bit checksum are split into 12 groups of 11 bits, each picking one word. Pasting the phrase into Validate Mnemonic confirms the checksum.

BIP39 Word Count, Entropy and Checksum

WordsEntropy bitsChecksum bitsTotal bits
121284132
151605165
181926198
212247231
242568264

Per BIP39: checksum = entropy / 32 bits, and each word encodes 11 bits.

  1. Choose the phrase length: 12, 15, 18, 21 or 24 words.
  2. Click Generate Mnemonic to create a random BIP39 phrase.
  3. Read the words in numbered order.
  4. Copy the phrase with the copy button if you need it for a test.
  5. To check a test phrase, paste it into the Validate Mnemonic box and click Validate.
  6. Never share a real seed phrase or store it digitally in an unsafe place.

BIP39 Seed Phrases: Words, Entropy and Checksum

This tool generates BIP39 seed phrases of 12, 15, 18, 21 or 24 words and checks whether an existing phrase is valid. A 12-word phrase holds 128 bits of randomness and a 24-word phrase holds 256 bits. It is meant for learning, testing and development, not for wallets that will hold real money.

BIP39 turns random bits into words that are easy to write down. The tool takes 128 to 256 random bits from the Web Crypto API. It adds a short checksum taken from the SHA-256 hash of those bits and splits the total into groups of 11 bits. Each group picks one of the 2,048 words in the official English list. The list is built so the first four letters of each word are unique.

The checksum is what the validator tests. It catches most typos and swapped words. With 12 words, a random mistake fails the checksum 15 times out of 16, and with 24 words, 255 times out of 256. The validator also ignores capital letters and extra spaces. A valid result only means the phrase follows the standard. It does not show that a wallet exists or holds funds.

For a real wallet, let a hardware wallet or trusted offline wallet app create the phrase. A browser can be exposed to extensions, malware and clipboard snooping, even though this tool sends nothing to a server. Never type or paste the seed of a funded wallet into any website, including the validator here. The tool does not derive keys or addresses and does not support the optional BIP39 passphrase. For other random secrets, use the Token Generator.

Sources

Frequently Asked Questions

It is a list of 12 to 24 words from a standard list of 2,048 English words that encodes the master secret of a crypto wallet. From that one phrase, a compatible wallet can rebuild all its keys and addresses. Words are easier to write down and check than a long string of random characters.
Both are secure. Twelve words give 128 bits of randomness, which is far beyond any brute-force attack. Twenty-four words give 256 bits and a stronger checksum, and some hardware wallets use them by default. The real risk is not guessing but someone finding your written copy, so storage matters more than length.
Either a word is not on the BIP39 English list, the word count is not 12, 15, 18, 21 or 24, or the checksum fails. A checksum failure usually means one word is wrong or two words are swapped. Check spelling against the official list. A phrase from a wallet that uses another word list or standard will also fail.
For testing and learning, yes. For a wallet that will hold real funds, no. Any web page runs alongside extensions and other software that could read the screen or clipboard. Use a hardware wallet or official wallet software on a device you trust, ideally offline, and write the phrase on paper or metal.
They can restore your wallet on their own device and move all the funds, and crypto transactions usually cannot be reversed. Keep the phrase offline, never photograph it or store it in cloud notes, and never type it into a site or share it with anyone who asks, including people claiming to be support staff.

Related Tools

Password Generator

Generate strong, secure passwords with customizable length, character types, and multi-word passphrases.

Security and Encryption

Token Generator

Generate random tokens and strings in hex, alphanumeric, URL-safe, and custom character set formats.

Security and Encryption

Hash Generator

Create MD5, SHA-1, SHA-256, SHA-384 and SHA-512 hashes of text or files, right in your browser.

Security and Encryption

RSA Key Pair Generator

Generate RSA public and private key pairs in PEM format using the Web Crypto API in your browser.

Security and Encryption

Text Encryption and Decryption

Encrypt and decrypt text using AES-256 encryption entirely in your browser. No data sent to servers.

Security and Encryption