Readability Checker
Commercial use OK
380+ models
No watermark
No sign-up needed
Model:
+ GPT-5, Claude, Gemini
Runs fully in your browser — nothing sent to the server. Computes Flesch Reading Ease, Flesch-Kincaid Grade, Gunning Fog, SMOG, Automated Readability Index, and Coleman-Liau. Per-sentence highlights flag the hardest sentences.
Flesch Ease
—
0–100 scale
Flesch-Kincaid
—
grade level
Gunning Fog
—
grade level
SMOG
—
grade level
ARI
—
grade level
Coleman-Liau
—
grade level
Avg sentence length
— words
Avg syllables / word
—
Complex words (3+ syl)
—
Verdict & audience
Start typing to see readability analysis.
Per-sentence difficulty
Hardest sentences highlighted
Advanced options
Result
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Check text readability with free AI. Get grade level and improvement suggestions.
How to Use Readability Checker
1
Enter your input
Type text, upload a file, or describe what you want. No account needed.
2
Click generate
Our AI processes your request in seconds using the best open-source models.
3
Download & share
Download, copy, or share your result. Free for personal and commercial use.
Use this tool via API
Automate this tool from your own code. OpenAI-compatible REST endpoint, Bearer-token auth, no extra SDK required. Token costs match the web interface.
curl -X POST https://api.free.ai/v1/chat/ \
-H "Authorization: Bearer sk-free-..." \
-H "Content-Type: application/json" \
-d '{"model": "qwen7b", "messages": [{"role": "user", "content": "Summarize this: ..."}]}'Related Free AI Tools
Readability Checker — FAQ
Free.ai Readability Checker analyzes text and returns 6 standard readability scores: Flesch Reading Ease, Flesch-Kincaid Grade, Gunning Fog Index, SMOG Index, Automated Readability Index (ARI), and Coleman-Liau. Plus average sentence length, average syllables per word, complex-word count, and per-sentence difficulty highlighting. 100% browser-side — zero server calls, zero tokens used, text never leaves your device.
Hemingway Editor is $19.99 one-time desktop app with 4 grade bands. Readable.com is $4–$48/mo for batch analysis. WebFX has a free tool with just Flesch + FK. Grammarly Premium ($12/mo) shows readability inside its editor. Free.ai is completely free, zero sign-up, ships 6 readability formulas (more than all competitors), and runs entirely in-browser — your text never hits a server. We also link to our /text/simplifier/ for one-click rewrites when the score is too high.
Each formula captures slightly different signal. Flesch Reading Ease (0–100, higher = easier) is the classic for general content. Flesch-Kincaid Grade Level is US-school aligned. Gunning Fog emphasizes complex words (3+ syllables). SMOG was built for medical texts. ARI uses character count instead of syllables. Coleman-Liau is similar. The average across all 5 grade-level formulas is the most robust estimate — we show it in the verdict.
Four blind spots: (1) Vocabulary difficulty is approximated by syllables — a short-but-rare word ("quaff") scores easier than a long-but-common word ("application"), which is backwards. (2) Sentence complexity is not sentence length — a long clear sentence can score harder than a short confusing one. (3) Subject-matter difficulty is invisible to these formulas. (4) All formulas were calibrated on English prose — non-English scores are rough approximations.
Each weights different signals. Flesch-Kincaid and Gunning Fog usually agree within 1 grade for standard prose. SMOG tends to run 1–2 grades higher on technical text (it rewards complex-word reduction more heavily). ARI and Coleman-Liau use character count instead of syllables, so they score differently on very short or very long words. Average them for a robust estimate; trust agreement across 4+ formulas as a strong signal.
Depends on audience. General public: 8th grade (newspaper register). Mass-market blog or consumer content: 6th–8th. Professional business / B2B: 9th–12th. Academic / technical: 13th+ (college). US regulatory guidance recommends 7th–8th grade for public-facing documents. Plain-language laws (UK, Australia, US federal) require 8th grade or below.
Computes a Flesch-Kincaid grade for each sentence individually, then highlights the top 20% hardest. Useful for spot-editing — rewrite the highlighted sentences to shorter/simpler versions and your overall score drops fast. Hemingway Editor's famous feature, now free and client-side.
You can paste non-English text and scores compute, but the formulas were calibrated on English so results should be treated as approximations. For Spanish, Fernández-Huerta formula would be more accurate (not implemented here). For German, Amstad or Wiener Sachtextformel. For mixed-language documents, split into single-language chunks and analyze separately.
No — everything runs in your browser. Nothing is sent to any server. You can verify this in your browser's Network tab: no POST requests fire when you use the readability checker. Perfect for confidential or proprietary text.
No. Zero tokens, zero server calls. Completely free, no usage cap, no sign-up required.
We use a standard heuristic syllable counter (same approach as most readability libraries) that handles ~95% of English words correctly. Edge cases: silent E, compound words, proper nouns, loanwords. For research-grade accuracy you'd need a pronunciation dictionary (CMU or similar) — ours is good enough for practical use.
Readability Checker is client-side — no server endpoint. If you want programmatic readability analysis, the standard Python library "textstat" implements the same formulas. Our JS code is inspectable in the page source if you want to port it.
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