# Readability Check

> Paste English text and get its reading level free in the browser - Flesch Reading Ease, Flesch-Kincaid grade, Gunning Fog, SMOG, Coleman-Liau, Automated Readability Index, a consensus grade and an estimated CEFR level, with every word coloured A1 to C2. Then rewrite it to CEFR A2, B1, B2, C1 or US grade 3-12 while keeping every fact; the rewrite is re-scored, diffed word by word and checked for lost numbers and names. No API key needed: rewrites are paid per run with SkillSafe credits.

URL: https://readability-check.skillsafe.ai/

## What it does

- Free, in the browser, no sign-in: sentence, word and syllable counts; six published readability formulas and their median grade; a CEFR vocabulary profile (share of words at each level A1-C2 and words on no list); the estimated CEFR level (the higher of the vocabulary level at 95% coverage and a sentence-length band); the five hardest sentences; every word at B2 or above; a Markdown report and a CSV word list with levels.
- Paid (one model run): a rewrite to the chosen level that keeps every number, name and fact, lists its main changes (original words, new words, why), the terms it kept on purpose and anything worth checking.
- After the rewrite, the browser re-scores it, says whether the target was reached and why not, lists any number or name from the original missing from the rewrite, lists words still above the target that the rewrite did not declare as kept terms, and shows a word-by-word diff.
- Past rewrites are saved to the signed-in person's account.

## Input contract (run)

A flat JSON object: task ("rewrite"), text, target (A2, B1, B2, C1, G3-G10, G12), target_label, keep_terms, audience, prescan (JSON string of the free check), retry_note (only on the one reformat retry). Up to 1,500 words per run, cut between paragraphs.

## Output contract

One JSON object: task, status (ok | already_at_level | not_prose), message, target, level_read, rewrite, changes[{from, to, why}], kept_terms[{term, why}], check_notes[].

## Sources and licences

- Word levels A1-B2: The CEFR-J Wordlist Version 1.5, compiled by Yukio Tono, Tokyo University of Foreign Studies (free for research and commercial use with citation).
- Word levels C1-C2: Octanove Vocabulary Profile C1/C2 ver 1.0, Octanove Labs, CC BY-SA 4.0.
- Syllables: CMU Pronouncing Dictionary (BSD-style licence).
- Full terms: https://readability-check.skillsafe.ai/LICENSE.txt

## Limits

Readability formulas and word lists measure surface features (sentence length, word length, word frequency level); they are guides, not a test of any reader. The CEFR estimate is vocabulary- and sentence-length-based, not a trained classifier. Rewrites come from a language model and should be read before use.

## Pages

- App: https://readability-check.skillsafe.ai/
- API tutorial: https://readability-check.skillsafe.ai/api.html