Passphrase Generator
Generate secure random passphrases from a 256-word list using the Web Crypto API. Customize word count, separator, capitalization, and numbers. See entropy estimate. Free, 100% in your browser.
Reference
What is a passphrase?
A passphrase is a password made of random words instead of random characters. Passphrases like "correct-horse-battery-staple" are easier to remember than "Xy7!kQ9#" but can be equally or more secure due to their length. Security comes from the randomness of word selection, not from the words themselves. This tool uses a 256-word list and the browser's Web Crypto API for cryptographically secure random word selection.
How is entropy calculated?
Entropy measures the randomness (unpredictability) of a passphrase in bits. Each word selected from a 256-word list adds log₂(256) = 8 bits of entropy. A 5-word passphrase has ~40 bits of base entropy. Capitalizing each word adds ~1 bit per word (2 choices per word). Adding a random number (0-99) adds ~6.6 bits. A 5-word capitalized passphrase with a number has ~53 bits of entropy — comparable to a random 8-character password with mixed case, digits, and symbols. For high-security use, 6+ words (~56+ bits) is recommended.
Privacy
All generation uses the Web Crypto API and runs 100% in your browser. No data is sent to any server — your passphrases never leave your device.