SEO health is a 0–100 score Crawlinx computes from 157 technical checks run on every crawled page — indexability, titles and meta descriptions, canonical and hreflang correctness, internal linking, redirects, broken links and Core Web Vitals signals. A site scores high only when the whole crawl is clean, so a single median hides a spread worth reading below.
Across 5 Jekyll sites the median SEO health is 65, with the middle half falling between 65 (25th percentile) and 66 (75th percentile). The full range runs from 62 to 85. The tight range means most sites in this segment cluster near the median, so a score much below it points to a site-specific misconfiguration rather than a platform-wide limitation.
Because these sites share the Jekyll platform, they inherit the same defaults — its templating, URL structure, sitemap and meta handling — which is why they cluster. The remaining variance is down to theme, plugins and how each team configured them, so the most common issues below are the ones Jekyll does not solve out of the box and every Jekyll site owner should verify.
The single most common problem here is “Images without width/height (layout shift / CLS)”, present on 100% of the sample, followed by “Missing recommended security headers” and “Heading levels skip a level”. The full ranking is in the table above — fix the top of that list first, since it is the fault most likely to be dragging this segment's median down.