Shannon Entropy Calculator | String Entropy

Shannon entropy calculator for any string or text, in bits, nats or dits. Shows symbol frequencies, efficiency and which tokens look like secrets. Free. Designed specifically for developers and professionals, this free online calculator runs entirely in your browser to process tasks quickly and securely. Enjoy unlimited usage with no data tracking and no registration required.

Also known as: shannon entropy calculator · entropy calculator online · string entropy calculator · calculate entropy of a string · information entropy calculator · text entropy calculator · bits per character calculator · entropy of a password or api key

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Text Input

Count symbols as

Logarithm base

Entropy Results

Results will appear here: entropy per symbol, total information, efficiency, a frequency table and the highest-entropy tokens in your text.

About Shannon Entropy Calculator

Shannon Entropy Calculator measures how unpredictable a piece of text is, in bits per character, and is used to tell random-looking strings such as API keys and session secrets apart from ordinary words. Paste a string or a whole file to get the entropy, the total information content, the symbol frequency table, and every long token ranked by entropy with the thresholds secret scanners use.

Key Features

Computes H = -sum p(x) log p(x) in bits (base 2), nats (base e) or dits (base 10)
Counts symbols as Unicode characters or as UTF-8 bytes, which matters for emoji and non-Latin text
Reports total information, the maximum entropy for the alphabet used, and efficiency as a percentage
Ranks every 16+ character token by entropy and flags hex above 3.0 and base64 above 4.5 bits per character
Shows a full symbol frequency table with counts and probabilities
Runs entirely in your browser, so a password or key you are testing is never sent anywhere

Use Cases

Check whether a generated session secret is actually random before shipping it to production
Tune the entropy threshold for a Gitleaks or TruffleHog rule against real strings from your codebase
Explain to a teammate why a git SHA trips a secret scanner while a long config value does not
Compare the information content of two compression or encoding formats in a CS homework set
Spot a hardcoded token in a .env file that looks like configuration at first glance
Measure how much a UTF-8 byte view changes entropy for text containing emoji or accented names

Supported Formats

Plain text and strings

Passwords and API keys

.env and config files

JSON and log files

Unicode and emoji (character or byte mode)

Related Keywords

shannon entropy calculator

entropy calculator online

string entropy calculator

calculate entropy of a string

information entropy calculator

text entropy calculator

bits per character calculator

entropy of a password or api key

What is a good Shannon entropy for a password or API key?

It depends on the alphabet. A string that uses only hex digits cannot exceed 4 bits per character, and base64 tops out at 6, so compare against the maximum shown here rather than a single number. Secret scanners traditionally treat hex above 3.0 and base64 above 4.5 bits per character as suspicious. Remember that Shannon entropy measures one string's character mix, not how it was generated: aB3dE5gH7j scores high but is a pattern, so strength comes from a random generator, not from the score alone.

Privacy & Security

All processing happens locally in your browser. Your data never leaves your computer, ensuring complete privacy and security.

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Frequently asked questions

What is Shannon Entropy Calculator used for?

Shannon entropy calculator for any string or text, in bits, nats or dits. Shows symbol frequencies, efficiency and which tokens look like secrets. Free.

Is Shannon Entropy Calculator free to use?

Yes. Shannon Entropy Calculator is completely free with no usage limits, and there is no paid tier required to use it.

Do I need an account to use Shannon Entropy Calculator?

No. Shannon Entropy Calculator works immediately in your browser with no signup, login, or email address required.

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