What does the free SEO checker test?
The SEO checker is a free tool from VirtuoLab that downloads one page and runs more than 30 checks in six categories. First, the meta category checks a title of 30 to 60 characters, a meta description of 120 to 160 characters, five Open Graph tags, Twitter Card tags and a canonical link. Second, the content category looks for exactly one h1, at least two h2 headings, alt text on every image, structured data and at least five internal links. Fewer than 300 words gets a warning, and the best result starts at 600. Third, the technical category checks the lang attribute, UTF-8, a favicon and the robots meta tag. According to Google, a noindex rule drops a page from search results. Finally, performance, mobile and security cover response time, compression, the viewport tag, HTTPS and five security headers. The checker does not run JavaScript, so a page built with React may show fewer words. For example, a site with 20 pages needs 20 runs.
How is the SEO score calculated?
The SEO score is a weighted average of six category scores, each on a scale from 0 to 100. First, every category starts at 100 points, and each failed check deducts points. A missing title or meta description costs 25 points in the meta category, and a missing canonical link costs 15. A noindex tag costs 30 technical points, because the page then asks Google to stay out of the index. A missing viewport tag costs 35 mobile points. The total follows fixed weights: meta 25%, content 20%, technical 15%, performance 15%, mobile 15% and security 10%. For example, a page with perfect scores everywhere except a mobile score of 65 ends at 95 overall. A total of 90 or higher reads as Excellent, 70 to 89 as Good, 50 to 69 as Fair, and anything lower as Poor. Finally, the report lists every improvement next to every passed check, and a PDF download with VirtuoLab branding keeps the result for a developer.
What should you fix first after the SEO check?
The best first fix after an SEO check is any error that blocks indexing, such as a robots meta tag with noindex. Second, add a missing title, meta description or h1, since each one costs 25 points in its category. Third, look at speed. The checker measures server response time, and 800 milliseconds or more counts as slow. According to Google on web.dev, a good Largest Contentful Paint (LCP) is 2.5 seconds or less, measured at the 75th percentile of page loads. Only 48% of mobile sites passed all Core Web Vitals, according to the HTTP Archive Web Almanac 2025. On 76% of mobile pages, the LCP element is an image, so a smaller hero image in WebP or AVIF is a sensible start. Measure LCP using PageSpeed Insights, since the checker does not. Finally, add Open Graph tags, which control how a link looks when shared on LinkedIn or WhatsApp. For example, a missing og:image leaves a shared link without a preview picture.