Score Text Readability in 1 API Call — Free Flesch-Kincaid Analyzer (2026)

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Free Readability Score API - Analyze Text Complexity & Reading Level

Writing content that your audience can actually understand is hard. Sentences too long? Vocabulary too complex? You need to know the grade level and reading difficulty of your text before publishing. Tools like Hemingway Editor help visually, but don't provide scores via API. What if you could analyze text readability programmatically and get Flesch, Gunning Fog, SMOG, and Dale-Chall scores instantly?

The Readability Score API analyzes text and returns multiple readability metrics: grade level, reading difficulty (8th grade? PhD?), estimated reading time, vocabulary complexity, and improvement suggestions. Perfect for content optimization, educational assessment, accessibility compliance, and copywriting analysis.

Why Use This API?

Understanding text complexity matters:

• Content Marketing – Ensure your blog posts are accessible to your target audience
• Education – Verify student writing is at grade level
• Accessibility – Meet WCAG guidelines for readable content
• Legal/Medical – Simplify complex documents for compliance

Quick Example - cURL

# Analyze text readability
curl -X POST "https://readability-score-api.p.rapidapi.com/analyze" \
  -H "X-RapidAPI-Key: YOUR_KEY" \
  -H "X-RapidAPI-Host: readability-score-api.p.rapidapi.com" \
  -H "Content-Type: application/json" \
  -d '{
    "text": "The quick brown fox jumps over the lazy dog. This pangram is often used for font testing and keyboard layout demonstration."
  }'

Response:

{
  "success": true,
  "word_count": 24,
  "sentence_count": 2,
  "syllable_count": 38,
  "average_word_length": 4.5,
  "average_sentence_length": 12,
  "flesch_reading_ease": 78.5,
  "flesch_kincaid_grade": 4.2,
  "gunning_fog_index": 5.1,
  "smog_index": 7.8,
  "dale_chall_score": 7.2,
  "grade_level": "4th-5th Grade",
  "reading_difficulty": "Easy",
  "estimated_reading_time_seconds": 12
}

Python Example

import requests

url = "https://readability-score-api.p.rapidapi.com/analyze"
headers = {
    "X-RapidAPI-Key": "YOUR_API_KEY",
    "X-RapidAPI-Host": "readability-score-api.p.rapidapi.com",
    "Content-Type": "application/json"
}

# Analyze blog post for accessibility
blog_text = """
Artificial intelligence has profoundly transformed numerous industries and societal constructs...
[longer text here]
"""

response = requests.post(url, json={"text": blog_text}, headers=headers)
data = response.json()

print(f"Grade Level: {data['grade_level']}")
print(f"Reading Difficulty: {data['reading_difficulty']}")
print(f"Flesch Reading Ease: {data['flesch_reading_ease']}/100")
print(f"Est. Reading Time: {data['estimated_reading_time_seconds']}s")

if data['flesch_reading_ease'] < 50:
    print("⚠️  WARNING: Text is too complex. Simplify for better engagement.")

JavaScript / Node.js Example

const axios = require("axios");

const analyzeReadability = async (text) => {
  const response = await axios.post(
    "https://readability-score-api.p.rapidapi.com/analyze",
    { text },
    {
      headers: {
        "X-RapidAPI-Key": process.env.RAPIDAPI_KEY,
        "X-RapidAPI-Host": "readability-score-api.p.rapidapi.com"
      }
    }
  );

  const {
    grade_level,
    flesch_reading_ease,
    reading_difficulty,
    word_count,
    estimated_reading_time_seconds
  } = response.data;

  return {
    grade_level,
    difficulty: reading_difficulty,
    score: flesch_reading_ease,
    words: word_count,
    reading_time: estimated_reading_time_seconds
  };
};

// Check if content meets accessibility standards
const content = "Check that your writing is clear and accessible...";
analyzeReadability(content).then(metrics => {
  if (metrics.difficulty === "Hard") {
    console.log("Simplify this content for better accessibility");
  } else {
    console.log("✅ Content passes readability check");
  }
});

Understanding the Scores

Flesch Reading Ease (0-100)

• 90-100: Very Easy (5th grade)
• 60-70: Standard (8th-9th grade)
• 30-50: College level
• 0-30: College graduate

Flesch-Kincaid Grade

The grade level needed to understand the text. e.g., 6.2 = 6th grade, 2nd month.

Gunning Fog Index

Years of formal education needed to understand. Higher = harder.

SMOG Index

Grade level needed to understand 90% of content.

Dale-Chall Score

9.9-12.9 = 9th-12th grade
13+ = College level

Real-World Use Cases

1. Blog Post Optimization

Ensure your article is at the right reading level for your audience. Adjust complexity before publishing.

# Check if article is too complex for target audience
if data['grade_level'] > 'College' and target_audience == 'high school':
    suggestion = "Simplify technical jargon and use shorter sentences"

2. Educational Assessment

Teachers verify student writing is at grade level. Detect if text is too simple or too complex.

3. Accessibility Compliance

Ensure content meets WCAG guidelines for readability. WCAG AA requires max grade 9, AAA requires max grade 6.

4. Legal/Medical Document Simplification

Simplify contracts and medical instructions to be understandable by the general public.

5. Email Subject Line Analysis

Check if email subject is clear and easy to scan.

6. Product Copy Optimization

Ensure product descriptions, CTAs, and marketing copy are easy to understand for your audience.

Pricing

Plan	Cost	Requests/Month	Best For
Free	$0	500	Writing analysis, testing
Pro	$5.99	50,000	Content marketing teams
Ultra	$14.99	500,000	Educational platforms

Related APIs

• Text Analysis API – Sentiment, keywords, entities
• Text Summarizer API – Create summaries to reduce complexity
• Grammar Checker API – Fix grammar for clarity
• Text Diff API – Compare original vs. simplified versions

Get Started Now

Analyze readability free on RapidAPI

No credit card. 500 free requests to analyze text complexity and grade level.

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Writing for a specific audience? Share your target grade level in the comments!