What is the BIP39 Generator?
The BIP39 Generator on Toolsdevelop is a free, browser-based tool that creates BIP39 mnemonic phrases (seed phrases) for cryptocurrency wallets and HD wallets. BIP39 (Bitcoin Improvement Proposal 39) defines the standard for generating human-readable mnemonic codes from a random entropy source. This tool produces a 12, 18, or 24-word seed phrase using the official BIP39 wordlist (2048 words). Each phrase is cryptographically secure, compliant with the BIP39 specification, and includes the correct checksum (the last word is partially derived from a SHA-256 hash of the entropy).
Unlike many online generators that send data to a server, this tool runs entirely client-side using JavaScript's crypto.getRandomValues() for high-quality randomness. Your entropy and generated phrase never leave your device. No account, no email, no tracking—just pure, private generation. This is essential for anyone handling real cryptocurrency funds, as any exposure of the seed phrase can lead to theft.
The tool is ideal for developers testing wallet implementations, security-conscious users creating a new wallet, or educators demonstrating BIP39 mechanics. It also supports generating multiple phrases in one click, making it useful for bulk testing or generating test vectors.
How the BIP39 Generator Works
The generation process follows the exact BIP39 algorithm:
- Entropy Generation: The tool uses the browser's
crypto.getRandomValues()to generate cryptographically secure random bytes. For a 12-word phrase, it generates 128 bits of entropy; for 18 words, 192 bits; for 24 words, 256 bits. - Checksum Calculation: The entropy is hashed using SHA-256. The first
ENT/32bits of the hash are appended to the entropy as a checksum. For example, 128 bits of entropy → 4 bits of checksum. - Mnemonic Encoding: The combined entropy+checksum is split into 11-bit segments. Each segment is an index into the BIP39 wordlist (0–2047). The corresponding words are concatenated with spaces to form the seed phrase.
- Output Display: The generated phrase is displayed in a text area, with a copy button and a 'Generate New' button. The tool also shows the entropy in hex and the seed (if you choose to derive it) for advanced users.
All operations are performed locally. The tool does not use any external libraries that might introduce vulnerabilities—it relies on the Web Crypto API, which is widely supported in modern browsers.
Why Use a Client-Side BIP39 Generator?
Security is the primary concern when generating seed phrases. If you generate a phrase on a server-based website, the server could log your phrase, and you'd never know. Even if the site claims to be secure, you're trusting a third party with your funds. With Toolsdevelop's BIP39 Generator, the phrase is generated in your browser and never transmitted. This eliminates the risk of interception, server-side logging, or malicious code.
Additionally, the tool is open and transparent—you can inspect the source code (view page source) to verify that no data is sent. The Device Information tool shows that we value transparency and client-side operations across all our tools.
Another advantage is offline capability. While the tool is hosted online, you can save the page or use it in an offline browser environment (e.g., after downloading the HTML) to generate phrases without any internet connection. This is a recommended practice for high-security wallets.
Use Cases for the BIP39 Generator
1. Creating a New Cryptocurrency Wallet: When setting up a new wallet (e.g., Bitcoin, Ethereum, or any BIP39-compatible coin), you need a seed phrase. Use this generator to create a truly random phrase, then import it into your wallet software.
2. Testing Wallet Software: Developers can use this tool to generate test vectors, verify BIP39 implementations, or create deterministic wallets for testing. The tool allows generating multiple phrases quickly, which is handy for unit tests.
3. Education and Demos: Teachers and content creators can show how BIP39 works, how entropy translates to words, and how checksums are calculated.
4. Backup and Recovery Testing: You can generate a phrase and test recovery in a wallet, ensuring your backup process works before trusting it with real funds.
For related encoding tasks, you might also need a Base64 String Converter or a Base64 File Converter for handling other data formats.
Understanding BIP39 Wordlist and Checksum
The BIP39 wordlist consists of 2048 carefully selected words that are easy to remember and hard to confuse (e.g., 'abandon', 'ability', 'able'). Each word maps to a unique 11-bit index. The checksum ensures that a mistyped word is detected. For a 12-word phrase, the checksum is 4 bits; for 24-word, it's 8 bits. This means the last word is not entirely random—it contains a portion of the SHA-256 hash of the entropy.
This tool uses the official BIP39 English wordlist. It does not support other languages (e.g., Spanish, Japanese) yet, but the English list is the most widely used. The generated phrase is fully compatible with all BIP39 wallets, including Ledger, Trezor, MetaMask, and others.
If you're working with other security-related tools, check out our Bcrypt Hash Generator for password hashing, or the Basic Auth Generator for HTTP authentication headers.
Technical Specifications and Security Features
- Entropy Sources: Uses
crypto.getRandomValues()—a cryptographically secure random number generator (CSPRNG) provided by the browser. This meets the security requirements of BIP39. - No Server Interaction: The entire generation process happens in your browser. No network requests are made except for loading the page itself.
- No Data Storage: The tool doesn't store any generated phrases, entropy, or seeds. Once you leave the page, everything is gone.
- Support for Word Counts: You can choose 12, 18, or 24 words. The corresponding entropy sizes are 128, 192, and 256 bits respectively.
- Copy to Clipboard: A one-click copy button lets you copy the phrase securely. Note that clipboard access is also client-side.
For developers, the tool also outputs the entropy in hexadecimal, which is useful for debugging or for use in custom scripts. You can also convert the phrase to a seed (using PBKDF2) if you need the 64-byte seed for HD wallet derivation, though this is optional.
If you're building a pipeline that involves encoding, consider our Case Converter for text formatting, or the Color Converter for design tasks.
How to Use the BIP39 Generator Effectively
Using the tool is straightforward:
- Select the number of words: 12, 18, or 24.
- Click the 'Generate' button. The tool will create a new phrase instantly.
- Copy the phrase using the copy button or manually select and copy.
- Store the phrase in a secure offline location (e.g., a hardware wallet or a metal backup).
For optimal security, always generate phrases on a device that is free of malware and ideally offline. You can use the Device Information tool to check your browser's security features. Also, ensure you're using a trusted network to download the page, but after that, you can disconnect from the internet.
Never share your seed phrase with anyone. Anyone with your phrase can steal your funds. If you suspect a phrase has been compromised, transfer your assets to a new wallet immediately.
Frequently Asked Questions
We've compiled common questions about BIP39 generation, but you can also find more in the FAQ section below. For other utilities, explore our Crontab Generator or Chmod Calculator.
Conclusion
The BIP39 Generator is an essential tool for anyone involved in cryptocurrency. It's free, private, and secure. By generating phrases client-side, we ensure your seed phrases remain confidential. Whether you're a beginner setting up your first wallet or a developer testing BIP39 implementations, this tool meets your needs. Try it now and experience the peace of mind that comes with a truly private generator.
For more developer tools, visit Toolsdevelop and explore our collection of Benchmark Builder, Docker Run to Docker Compose Converter, and Camera Recorder.