Meter estimates how strong a password is — how much randomness it carries and roughly how long it would take a fast attacker to guess — and points out weaknesses like being too short or too predictable. What you type is never sent anywhere. It stays in this page.

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characters

bits of entropy

character set

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to crack (offline)

The estimate is based on length and the mix of character types, minus penalties for common patterns like sequences, repeats and dictionary-ish words — it can't know if a password has appeared in a breach, so treat a strong score as necessary, not sufficient. Nothing you type is transmitted, logged or stored. Everything runs on your device.