Readability Checker: Analyze and Optimize Your Text

Whether self-written, supplied by others, or AI-generated – every text has an audience, and every audience has different requirements for comprehension. A medical journal article can be more complex than an online shop product description.

This tool analyzes your text using six proven readability formulas – from the Flesch index to the Vienna factual text formulas to the LIX and HIX indices. Additionally, the problem spots analysis highlights overly long sentences and complex words directly in the text, so you can immediately see where optimization is needed.

How the Readability Checker Works

1. Paste text: Copy your text into the input field (up to 20,000 characters). Analysis starts automatically.
2. Fetch a URL: Alternatively, enter a URL. The tool automatically extracts the main content from the page’s <main> or <article> element.
3. Read the quick overview: You’ll instantly see the key metrics: Flesch Reading Ease, Flesch-Kincaid Grade Level, Vienna Factual Text Formulas (1–4), LIX, and HIX.
4. Use the detailed analysis: Switch to the detailed view for character, word, and sentence statistics, estimated reading time, and the 20 most frequent words.
5. Check problem spots: In the “Problem spots” section, you’ll see your text with color highlights: yellow for sentences over 20 words, orange for sentences over 30 words, and red-underlined complex words.

What Do the Individual Metrics Mean?

• Flesch Reading Ease (0–100): The higher the value, the easier the text is to read. A score above 60 is considered easily understandable for the general public.
• Flesch-Kincaid Grade Level: Indicates the school grade level at which the text becomes understandable. A value of 8 means: from 8th grade onward.
• Vienna Factual Text Formulas (1–4): Developed specifically for German texts. The values indicate the school grade level at which a text becomes comprehensible.
• LIX (Björnsson): A cross-language index. Below 30 = very easy, 30–40 = easy, 40–50 = medium, 50–60 = difficult, above 60 = very difficult.
• HIX (Hohenheim Index, 0–20): Developed at the University of Hohenheim. Values of 10+ are considered easily understandable, 15+ very good.

Changelog

• Added LIX index (Björnsson formula) and HIX index (Hohenheim Index) as additional readability formulas
• Problem spots analysis: color highlighting of overly long sentences and complex words directly in the text
• URL fetching with automatic content extraction from main content areas
• Added frequency analysis of the 20 most-used words with visual display
• Stop word filter for word frequency analysis

Background: Why Readability Matters for SEO and User Experience

A text’s readability directly influences how long visitors stay on your page and whether they take the desired action. Studies show: users scan online text. If the first paragraph is too complex, they leave – regardless of how valuable the content behind it is.

Readability and SEO

Google measures user experience through signals like dwell time, scroll depth, and bounce rate. An understandable, well-structured text gets read longer and shared more often. These are indirect ranking factors that positively impact your visibility.

What Should You Do With the Results?

• Match your audience: A Flesch score of 30 is appropriate for a scientific article but too low for a blog post. Orient yourself to your readership.
• Shorten overly long sentences: Sentences with more than 20 words are harder to process. Split them up or remove filler words.
• Replace complex words: If a simpler synonym exists and the context allows it, use it.
• Keep paragraphs short: Online readers prefer short paragraphs of 2–4 sentences.
• Use as a benchmark: Also analyze your competitors’ texts to get a feel for the industry-standard level.

Frequently Asked Questions

What Flesch score is ideal?

For general web content, values between 50 and 70 are recommended. This corresponds to a slightly to moderately difficult text that’s easily understandable for most adults. For technical texts, lower values may be appropriate.

Does the tool only work for German texts?

The Flesch and LIX formulas work across languages in principle. However, the Vienna Factual Text Formulas and the HIX index were developed specifically for the German language. For English texts, Flesch and LIX are the most relevant metrics.

Why are some words marked as “complex”?

The tool marks words with three or more syllables as complex. This is an established indicator from readability research. Not every marked word needs to be replaced – technical terms that your audience knows are fine.

What does the reading time indicate?

The estimated reading time is based on an average reading speed of 200–250 words per minute. It gives you an indication of whether your text has the right length for the planned format (blog post, product page, whitepaper).

Can I analyze text from another website?

Yes. Enter the URL, and the tool automatically extracts the main content. This is especially useful for competitive analysis or evaluating reference pages for readability.

What do the colors in the problem spots analysis mean?

Yellow marks sentences with more than 20 words – still acceptable but could be shortened. Orange marks sentences with over 30 words – clear action needed. Red-underlined words are complex (3+ syllables) and could potentially be replaced with simpler alternatives.