How to use: Index of Coincidence

Index of Coincidence is a free online Text Tools tool that index of Coincidence (IC) is the probability of two randomly selected characters being the same. This can be used to determine whether text is readable or random, with English text having an IC of around 0.066. IC can therefore be a sound m instantly in your browser. Paste your data, adjust the options and get the result in real time — no installation, no sign-up, and nothing is ever uploaded to a server.

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Description

Index of Coincidence (IC) is the probability of two randomly selected characters being the same. This can be used to determine whether text is readable or random, with English text having an IC of around 0.066. IC can therefore be a sound m

  • Text Tools
  • Because everything is computed client-side, Index of Coincidence is safe to use with sensitive data such as API keys, tokens or private logs.
Input Index of Coincidence Output Runs 100% in your browser — your data never leaves your device.
Index of Coincidence — Input → Output

How to use

Using Index of Coincidence takes three steps:

  1. Paste your data into the input box (or load the example).
  2. Configure the options to match your target format or scenario.
  3. Copy, download or inspect the output — it updates live as you type.
How to use · Index of Coincidence 1 Paste your data intothe input box (or loadthe example). 2 Configure the optionsto match your targetformat or scenario. 3 Copy, download orinspect the output —it updates live as youtype.
How to use

Run

Use cases

Common situations where Index of Coincidence helps:

  • Index of Coincidence (IC) is the probability of two randomly selected characters being the same. This can be used to determine whether text is readable or random, with English text having an IC of around 0.066. IC can therefore be a sound m

Parameters

This tool has no options — it works on the input alone.

FAQ

What is Index of Coincidence?

Index of Coincidence index of Coincidence (IC) is the probability of two randomly selected characters being the same. This can be used to determine whether text is readable or random, with English text having an IC of around 0.066. IC can therefore be a sound m. It runs entirely in your browser, so your data stays private.

Is Index of Coincidence free to use?

Yes. Index of Coincidence is free, unlimited and works without registration or installation.

Does my data get uploaded?

No. All processing happens locally in your browser; nothing is sent to any server.

Good to know

  • Everything runs client-side, so extremely large inputs are limited by your browser tab’s memory rather than by a server upload limit.
  • The worked example below could not be pre-computed for this tool (threw: function is not iterable (cannot read property Symbol(Symbol.iterator))); the interactive tool above still works normally.

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