BIP39 Seed Phrase Generator

How to Use the BIP39 Seed Phrase Generator

The BIP39 seed phrase generator runs in your browser and lets you generate a mnemonic phrase or check a phrase you already have. When you open the page, the tool immediately generates a phrase for 12 words and checks its checksum, so you can see how it works without extra clicks.

How to use the tool:

1. Choose the number of words: 12, 15, 18, 21, or 24. The default is 12.
2. Click 'Generate new phrase' if you want a new set of words. The result appears in the Phrase field.
3. You can also paste your own phrase in the Phrase field if you want to check it. Do not paste the phrase of a wallet that holds funds there.
4. Click 'Check checksum'. The tool will count the words and show whether the phrase is valid.
5. If the phrase is valid, click 'Show seed (512 bits)'. Before showing the seed, you can enter an optional BIP39 passphrase in the 'Optional BIP39 passphrase (25th word)' field.

For the default values, 12 words and the phrase amazing eye gravity song above jaguar goose senior arm common critic phone, the tool shows a warning: ⚠️ Educational tool. Keys are generated locally in your browser and are never sent anywhere, but a website is not a safe place for keys to real money. Do not paste the recovery phrase of a wallet that holds funds here. For real savings, use a hardware wallet or run such tools offline. After checking, you will see: Phrase ✓ valid (12 words, 128 bits of entropy + 4 checksum bits). This confirms that the default phrase passes the BIP39 check.

What Is a BIP39 Seed Phrase and Checksum?

A BIP39 seed phrase is a set of words that represents randomness later used to restore a wallet. BIP39 describes how to write that randomness as words and how to add a checksum. This makes the phrase easier to write down and retype than a string of bits, but you still need to protect it like a key.

The checksum is extra bits appended to the randomness. Its job is to detect a typo, a missing word, or words in the wrong order. The tool counts the words, checks the checksum, and shows whether the phrase is valid. For a valid phrase, you will see the number of words and information about the entropy and checksum bits.

BIP39 Passphrase (25th Word) and Its Effect on the Seed

The 'Optional BIP39 passphrase (25th word)' field lets you add a passphrase to the phrase. In BIP39, this passphrase is sometimes called the 25th word, but it is not one of the words written in the phrase. It is an extra element that affects the final seed.

If you leave the field empty, the seed depends only on the phrase. If you enter a passphrase, the same set of words will produce a different seed than it would without the passphrase. In practice, this means that having the phrase alone may not be enough to restore a wallet if you use a BIP39 passphrase. You need to write down and store the passphrase just as carefully as the phrase.

The tool shows the 512-bit seed only after it checks the phrase. The phrase is then treated consistently: capitalization and extra spaces do not change the result. The BIP39 passphrase is taken into account when creating the seed. It cannot be recovered from the words alone, so do not lose it if you decide to use one.

Safe Generation and Storage of Your Phrase

The tool is educational. Keys are generated locally in your browser and are never sent anywhere, but a website is not a safe place for keys to real funds. To store savings, use a hardware wallet, and run similar tools offline when you want more control over the environment.

• Never paste the phrase of a wallet that holds funds. Anyone who knows the phrase or private key has full access to the funds.
• Do not use a phrase generated on a website to store real savings. Treat it as material for learning, testing on test networks, or checking wallet compatibility with a public test vector.
• Write down the phrase and optional BIP39 passphrase in a durable, private way. Do not do this in places where someone unauthorized can access them.
• Check that your device and browser are up to date and that no malicious software is running on them. The quality of the generated phrase also depends on the security of the environment where you create it.
• If you use the phrase with a hardware wallet, follow the manufacturer's instructions and do a test restore with a small amount or on a test network.

Tool Limitations and What It Does Not Calculate: Addresses and Paths

The tool generates a BIP39 phrase, checks its checksum, and after validation shows the 512-bit seed. That is all. It does not create addresses, derive public or private keys for specific networks, or calculate derivation paths. It does not connect to a blockchain, check balances, handle transactions, or act as a financial calculator.

A valid checksum only means that the phrase complies with BIP39. It does not mean the phrase is unused, that no one else uses it, or that it is safe for storing large funds. You also cannot check here whether a given wallet will use the exact same way of deriving addresses. Compatibility with a specific wallet is best checked with a public test vector and according to the wallet's instructions.

The tool supports phrases of 12, 15, 18, 21, and 24 words. It does not support other lengths or custom word lists. It does not replace a wallet and does not store your data. Everything you see is generated locally in your browser while you use the page.

Frequently Asked Questions

This tool is an auxiliary BIP39 generator/validator and does not charge fees; before using a seed, verify BIP39 compliance and store the phrase and passphrase in a safe offline place.