Entropy Calculator
Measure the Shannon entropy of any text or file (bits per byte) and estimate the effective strength of passwords — entirely in your browser.
Measure a repetitive string
Paste a low-entropy, repeating string to see how its Shannon entropy falls far below the 8 bits/byte maximum.
Repeated characters compress well, so the LZ token count also stays low. Random data approaches 8 bits per byte.
FAQ
What is Shannon entropy?
It measures how unpredictable a sequence is — how much information, in bits, each character carries on average. Fully random data scores about 8 bits per byte; predictable text scores far lower.
Is higher entropy always better?
For data you want to be unpredictable — passwords, keys, random tokens — yes, higher is better. Low entropy means patterns an attacker could guess.
What does the LZ (Lempel-Ziv) metric measure?
It counts how many unique subsequences a compression-style algorithm finds. Highly repetitive text produces few tokens; random text produces many — another way to judge compressibility and unpredictability.
How do I use this for passwords?
The calc measures the text you enter. Combine it with the Password Strength Checker for a fuller picture; entropy alone doesn’t account for whether your password is already in a breach list.