How to use the Character Frequency Counter
Last verified 2026-08-09 · about 6 minutes to read
The short version
- 1.Paste your text. An article for keyword density, or a ciphertext for cryptanalysis.
- 2.Choose what to count. Characters with "letters only" for cipher work. Words or phrases with stop words removed for content analysis.
- 3.Read the deviation column. It shows how far each letter is from its normal frequency in English — the core signal when breaking a substitution cipher.
Why this is worth getting right
Two audiences reach for this tool and competitors serve only one. Cryptanalysts need the frequency compared against the English baseline and the index of coincidence; writers need word and phrase density. Both are here, along with a Unicode category breakdown that reveals the emoji and punctuation you did not know were in the text.
Method 1 — use the Character Frequency Counter on this site
The fastest route. It runs entirely in your browser, so nothing is uploaded and there is no queue to wait in. No account is needed and there is no daily limit.
- Paste your text. An article for keyword density, or a ciphertext for cryptanalysis.
- Choose what to count. Characters with "letters only" for cipher work. Words or phrases with stop words removed for content analysis.
- Read the deviation column. It shows how far each letter is from its normal frequency in English — the core signal when breaking a substitution cipher.
Open the Character Frequency Counter →
Method 2 — do it without this site
Worth knowing, because a tool you cannot replace is a dependency rather than a convenience. Most tasks in the text division have a command-line or built-in equivalent; it is usually more setup and less convenient, but it works offline and it is scriptable, which matters once you are doing something a hundred times instead of once.
What this tool will not do
Every tool has an edge. These are ours for character frequency counter, stated up front so you find out here rather than halfway through a deadline:
- The baseline and the index of coincidence are English-specific. Other languages have different distributions and the comparison is meaningless for them.
- Frequency analysis needs volume. Below roughly 200 letters the distribution is too noisy to break a cipher with.
- Stop-word removal uses an English list only.
Questions people ask
What is the most common letter in English?
E, at about 12.02% of letters, followed by T at 9.10% and A at 8.12%. The figures used here are from Robert Lewand's Cryptological Mathematics (2000), which is the standard reference set in classical cryptanalysis.
How does letter frequency help break a cipher?
In a simple substitution cipher each plaintext letter maps to one ciphertext letter, so the frequency distribution is preserved — just relabelled. The most common ciphertext letter is very likely E, the next T. The deviation column ranks candidates for you.
What is the index of coincidence?
The probability that two letters picked at random from the text are the same. English prose sits near 0.067; random text near 0.038. A ciphertext near 0.067 is probably a simple substitution; one near 0.038 is probably polyalphabetic, like Vigenère — which tells you which attack to use.
Can I use this for keyword density?
Yes — switch to words, turn on "ignore common words", and read the percentage column. Two-word and three-word phrase counts are usually more informative than single words for content work.
Does it handle non-English text?
Counting works for any script — Bangla, Arabic, CJK and emoji are all counted correctly as grapheme clusters. The deviation column is English-specific and is left blank for characters outside the Latin alphabet.
How are emoji and accented letters counted?
As single characters. A family emoji is one entry, not seven, because the counter works on grapheme clusters rather than code points.