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 630 Next.js 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 31 to 93. That wide gap says the segment is not uniformly good or bad — platform defaults set a baseline, but individual configuration decides where a site lands. Compare your own score against the 75th percentile, not the median, to see what a well-run peer looks like.
Because these sites share the Next.js 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 Next.js does not solve out of the box and every Next.js site owner should verify.
The single most common problem here is “Missing recommended security headers”, present on 89% of the sample, followed by “Low text-to-HTML ratio” and “Thin content (low word count)”. 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.