Bitcoin Seed Phrase Generator
Last updated: | Educational browser tool with offline HTML option
Generate a 12, 18, or 24-word recovery phrase to learn how Bitcoin wallet seed phrases, entropy, checksums, and BIP-39 word counts work.
How does this Bitcoin seed phrase generator work?
| Word count | Entropy | Common use |
|---|---|---|
| 12 words | 128 bits plus checksum | Common recovery phrase length for many modern wallets. |
| 18 words | 192 bits plus checksum | Middle option for learning higher-entropy mnemonic phrases. |
| 24 words | 256 bits plus checksum | Common default for many hardware-wallet workflows. |
This tool generates a BIP-39 style Bitcoin recovery phrase (12, 18, or 24 words) within your browser environment. Generating a seed phrase is the most critical step in self-custody; whoever controls these words controls the Bitcoin attached to them. Treat browser-generated phrases as educational unless you have verified the full offline environment and security workflow yourself.
Local Entropy (Randomness): Powered by
crypto.getRandomValues(), a cryptographically secure random number generator
(CSPRNG) built directly into modern browsers. It pulls high-quality entropy (128, 192, or
256 bits) generated by your device’s
hardware noise, completely avoiding weak predictable algorithms like
Math.random(). Crucially, no external servers are contacted
during this process.
Embedded Wordlist: Uses the official 2048-word BIP-39 English list, stored directly in this file. No network fetches mean no risk of tampering or interception.
Checksum Protection: Adds a checksum (4, 6, or 8 bits, based on word count) from a SHA-256 hash of the entropy. This makes your phrase valid and verifiable by standard wallets.
Offline Security: Download the standalone HTML version, then open it locally with your browser disconnected from the internet. Running it offline eliminates network leaks. For extra safety, use a clean browser with no extensions.
Wallet Compatibility: Your generated seed phrase works with most BIP-39 compliant wallets. Hardware wallets like Ledger (24 words default), Trezor (12 or 24 words), and KeepKey fully support it. Software wallets like Electrum, Blockstream Green, Coinomi, and Trust Wallet also recognize these phrases.
Safety Notes: The phrase clears automatically after 5 minutes for your protection. For real funds, always consider a hardware wallet or a dedicated offline tool over a browser-based solution.
Bitcoin Seed Phrase FAQ
What is a Bitcoin seed phrase?
A seed phrase is a human-readable list of words used by compatible wallets to recover wallet access and private keys.
Can this run offline?
Yes. Download the standalone HTML file, disconnect from the internet, and open it locally in a clean browser.
Should I use it for real funds?
For significant funds, use a reputable hardware wallet or audited wallet process instead of relying only on a web tool.