Letter Frequency Analyzer

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Frequency Distribution

What is Letter Frequency Analysis?

Letter frequency analysis is the study of how often different letters appear in a text. Every language has characteristic letter frequencies—in English, the letter E appears most frequently, followed by A, R, and I. This property makes frequency analysis a powerful tool for cryptography, linguistics, and language detection.

Our Letter Frequency Analyzer automatically counts each character in your text and displays the results as percentages and visual charts, making it easy to spot patterns and compare against known language benchmarks. It works with any script — just remember that the "Letters Only" option restricts the count to A–Z, so untick it for Chinese, Japanese, Korean and other non-Latin text.

How to Use the Letter Frequency Analyzer

1. Enter Your Text: Paste or type any text into the textarea. It can be a paragraph, an entire document, or encrypted text.

2. Choose Your Options: Toggle case sensitivity (treat uppercase and lowercase as different), switch between letters-only (A–Z) or all-characters mode, and decide whether to compare against English frequency averages. To analyse Chinese, Japanese or Korean, untick "Letters Only" — that option keeps only the 26 Latin letters.

3. View Results: See the frequency of each character displayed as a percentage and count, with a visual bar chart sorted by frequency.

4. Analyze Patterns: Use the most/least common character highlights and the English average overlay to identify linguistic patterns or cryptographic insights.

5. Export Data: Download your frequency analysis as a CSV file for further analysis in a spreadsheet or statistical tool.

Use Cases for Frequency Analysis

• Cryptography: Break simple substitution ciphers by comparing letter frequencies to known language patterns
• Language Detection: Identify the language of a text by comparing its frequency profile to reference languages
• Authorship Analysis: Examine writing style by studying individual character and word frequency patterns
• Text Mining: Discover which characters or letters are dominant in large datasets
• Linguistic Research: Study the distribution of letters across different text types, genres, or historical periods
• Data Quality: Detect anomalies in text encoding by checking for unusual character distributions

What does "case sensitive" mean?

When case sensitive is enabled, uppercase and lowercase letters are treated as different characters (A vs a). When disabled, all letters are converted to lowercase before analysis, so A and a are counted together.

Can I analyze non-English text?

Yes, but untick "Letters Only" first — that option keeps only A–Z, so Chinese, Japanese, Korean, Greek, Cyrillic and Arabic characters are all discarded. The English frequency overlay is English-specific and is only drawn when the chart actually contains A–Z letters. Honest note about the old behaviour: before 2026-07-26, pasting Chinese with "Letters Only" ticked (the default) showed nothing but zeros and said nothing at all about why. Now the tool tells you which option caused it.

What is the "Letters Only" option?

When enabled, only the 26 Latin letters (A–Z, upper or lower case) are analysed; numbers, punctuation, spaces and every non-Latin script are ignored. When disabled, every character in the text is included. Also fixed on 2026-07-26: with "Case Sensitive" and "Letters Only" both ticked, the filter used to strip lowercase letters as well, so "hello World" was reported as a single character. It now keeps both cases.

How do I use this to break a cipher?

If you have a substitution cipher, paste the encrypted text and analyze its frequency. Compare the results to English letter frequencies. The most common letter in the cipher likely corresponds to E, the second most to A, and so on. This helps you build a letter mapping to decrypt the message.

Can I compare my text to other languages?

Our tool currently shows English frequency averages. For other languages, you can disable the English average overlay and manually compare your text's frequencies to reference data you find elsewhere. Many linguistic resources provide frequency tables for different languages.

Is my data private?

Yes. All analysis happens entirely in your browser. Your text is never sent to any server. Once you refresh the page, it's completely deleted.