The 0-100 score
We weight each check by estimated SEO impact, then compute:score = 100 - sum(weight_i * severity_i) / max_possible
Severity ladder
- Critical — blocks indexing or ranking (broken redirects, noindex on money pages).
- High — measurable ranking loss (missing H1, slow LCP, thin content).
- Medium — best-practice violations.
- Low / Info — nice-to-have polish.