How letter frequency counter works
Letter frequency analysis counts how many times each letter of the alphabet appears in a body of text. It is the classic technique for breaking monoalphabetic substitution ciphers (Caesar, Atbash, simple keyword ciphers): in English the most frequent letters are usually E, T, A, O, I, N, so the most frequent ciphertext letter is a strong candidate for E.
This counter scans your text and tallies only alphabetic letters (A-Z), ignoring digits, punctuation, spaces, and symbols. By default it folds case so 'A' and 'a' count together; toggle case sensitivity to count them separately. Results are sorted by count descending, with each letter's percentage of all letters shown.
Compare the resulting distribution against the known English letter-frequency profile to identify likely plaintext mappings when attacking a cipher, or use it for text analysis, stylometry, and language detection. All processing happens in your browser — no text is uploaded.
Frequently asked questions
What is letter frequency analysis?
A method for breaking substitution ciphers by counting how often each letter appears in the ciphertext. Because some letters are far more common than others in normal English (E is the most frequent), you can match the most frequent ciphertext letters to the most frequent plaintext letters.
Does this counter include numbers and punctuation?
No. Only the 26 letters A-Z are tallied. Digits, punctuation, spaces, and other symbols are ignored so the percentages reflect the true letter distribution.
What does the case sensitivity option do?
When off (default), upper and lower case letters are counted together, so 'A' and 'a' both add to the same tally. When on, they are counted as separate entries, useful for studying capitalization patterns.
Can this break any cipher?
Letter frequency analysis defeats simple monoalphabetic substitution ciphers (Caesar, Atbash). Polyalphabetic ciphers like Vigenère need additional techniques, and modern encryption is unaffected. Use it as a learning and puzzle tool.
