The SEO Content Checker is a free online SEO content checker and Google SERP simulator tool. It evaluates on-page articles, markdown drafts, and HTML pages in real time, calculating Flesch Reading Ease scores, focus keyword densities, 1-word and 2-word N-gram frequencies, and H1–H6 heading hierarchy structure while previewing desktop and mobile search snippets.

Yes, 100%. All content analysis, readability scoring, keyword density extraction, and SERP simulation execute client-side inside your browser's JavaScript engine. No drafts, proprietary text, or target keywords are ever sent to external cloud servers or logged to databases.

Google desktop search results truncate titles when they exceed approximately 580 to 600 pixels (roughly 50 to 60 characters). Our SERP simulator uses a proportional pixel-width calculation engine based on Google's Arial font metrics to warn you with an interactive progress meter before your title gets cut off by an ellipsis (...) on desktop or mobile.

The readability engine computes the Flesch Reading Ease score (0–100 scale) and the Flesch-Kincaid Grade Level metric. Its algorithms analyze total word count, sentence length, and syllable counts per word to estimate the exact educational reading level required for readers to comprehend your article.

For healthy organic ranking without triggering Google keyword stuffing algorithms, aim for a focus keyword density between 1.0% and 2.5%. Our tool tracks exact keyword occurrences across your body text, H1 title, and first 100 words, alerting you if density falls below 0.5% (under-optimized) or exceeds 3.0% (over-optimized).

Search engine crawlers rely on clean heading semantics to understand document outline structure. Our validator parses all headings, checking that exactly one H1 tag exists, ensuring focus keywords appear in subheadings, and detecting skipped hierarchy levels (such as jumping from H1 directly to H3 without an intermediate H2).

When you press Alt+P (or click the Smart Clipboard button), the tool reads your clipboard and intelligently auto-detects structured content formats: JSON serialized audit state, HTML markup containing <title>, <meta>, and <h1> tags, or Markdown drafts. It parses and populates the title, description, focus keyword, and content fields instantly.

Press Alt+1 to copy a Markdown Audit Report, Alt+2 for JSON Diagnostic Payloads, Alt+3 for Clean Stripped Text, Alt+4 for HTML Meta and Open Graph Tags, Alt+5 for a Markdown Keyword Density Table, Alt+V to toggle 2-Column Split Studio view, and Alt+C to clear all inputs. Press Alt+K or ? to open the full Shortcuts Reference.

Yes. In the Developer API Code Studio modal, you can copy or download production-ready audit scripts in cURL, Python (Requests), Node.js (Axios), PHP (cURL), Go (net/http), and Ruby (net/http) to validate content quality, readability, and heading hierarchy programmatically against our backend API (/api/seo-content-checker/analyze).

By combining high-fidelity Google Desktop and Mobile SERP snippet previews with rigorous on-page technical diagnostics (meta description 120–160 chars, title 50–60 chars, image alt-text verification, internal vs external link ratios, and N-gram term frequency analysis), you eliminate snippet truncation and deliver search-intent-aligned copy that maximizes CTR and user dwell time.