Password Strength Checker — entropy & crack time
Check password strength with an entropy estimate and crack-time — entirely in your browser, never sent anywhere.
🔒 Runs entirely in your browser. Your input and output are never sent to a server or stored — fully private.
🔒 Checked entirely in your browser — your password is never stored, sent or logged.
About this tool
Check how strong a password is with an estimate of its entropy in bits and roughly how long it would take to crack by brute force. Type or paste a password to get instant feedback on what makes it weak or strong — it is analysed entirely in your browser and never sent anywhere.
Frequently asked questions
What is password entropy?
Entropy measures how unpredictable a password is, expressed in bits — each extra bit roughly doubles the number of guesses an attacker needs. It grows with both length and the variety of characters, so a longer password from a larger character set scores higher.
What makes a password strong?
Length is the biggest factor, followed by using a mix of character types and avoiding dictionary words, names and anything reused from another account. A long passphrase or a random string from a generator will almost always beat a short, clever-looking password.
Is my password sent to a server?
No. The password is analysed entirely in your browser and is never transmitted, logged or stored — so you can safely test even passwords you actually use.