Password Strength Checker

How it works

Before using a password for an important account, it's useful to check that it actually holds up against guessing or brute-force attempts. This tool locally analyzes the length of the entered password, the character categories present (lowercase, uppercase, digits, symbols), derives an entropy estimate in bits (the base-2 logarithm of the size of the alphabet used, multiplied by the length), then combines these criteria to display a qualitative score ranging from "weak" to "very strong".

Is this password sent somewhere to be checked?

No, never. Unlike some services that compare your password against a database of known leaks (which requires sending at least a hash to an external server), this tool makes no network calls: the length, composition and entropy calculations happen entirely in your browser via WebAssembly.

What is password entropy?

Entropy measures, in bits, the number of attempts an attacker would on average need to guess the password through pure brute force. The wider the alphabet used (by adding uppercase, digits, symbols) and the longer the password, the faster this value increases — with length generally having more impact than character diversity alone.

The analysis happens entirely in your browser via WebAssembly, with no network request — your password is never transmitted anywhere.