Letters Frequency Analysis Tool

Analyze letter and n-gram frequencies

Frequency analysis counts letters, bigrams, trigrams or four-grams. It is particularly useful for studying a long sample or a simple substitution cipher. The chart, table and exports all use the same calculated dataset.

Compare with a language

French, English, Spanish, German, Italian and Portuguese references provide a baseline. They are averages: vocabulary, subject and sample length can produce a different distribution without indicating an error.

Index of coincidence

The index of coincidence measures the probability that two characters selected from the sample are identical. It can help distinguish some distributions, but it cannot identify a cipher by itself.

Getting useful results

Use several sentences, explicitly choose whether accents, digits, spaces and punctuation should be preserved, and compare more than one hypothesis. Very short text produces unstable frequencies.