Password Strength Checker
Estimate password strength with entropy scoring, character-class coverage and blacklist checks. Runs locally — passwords never leave the browser.
Enter a password
Test a passphrase
Type a strong passphrase into the box and watch the entropy meter, character-class breakdown and improvement tips update live.
The example runs instantly — there is no button to press. It updates as you type.
FAQ
How is my password strength calculated?
It estimates entropy from the length and the character classes used (lowercase, uppercase, digits, symbols), then subtracts penalties for repeated runs of characters and caps the score if the password appears in a built-in list of the most common, already-leaked passwords.
What counts as a strong password?
Aim for at least 12 characters (16+ is better) that mix letters, digits and symbols, and aren’t a known password or a simple dictionary phrase. The tool flags anything below roughly 40 bits of entropy as weak.
Does my password leave my browser?
No. Everything — the entropy math and the common-password blacklist — runs locally in your browser. Nothing you type is sent to any server.
Why does it say my password is compromised?
If the verdict reads “Compromised”, the password matches an entry in the built-in list of the most common breached passwords. That means it is almost certainly already in attacker wordlists — stop using it.