Why the weights are not equal
A checkout that returns errors costs more than a missing meta description, so the two cannot count the same. Performance carries the most weight because it is the only category every visitor experiences on every page. SEO, security and accessibility are level with each other: each one decides whether a whole group of people can reach or use the site at all.
Uptime carries the least weight, which reads like an error until you see what happens when a site goes down. The incident, the alert and a critical issue all fire immediately and independently of the score. Nobody needs a number to be told the site is offline. The 10% is there to record erosion — the odd 502, the deploy that dropped requests for four minutes — rather than to report a catastrophe.
What moves each category
Performance — 30% of the total
Time to first byte, largest contentful paint, cumulative layout shift, total transfer size and the number of render-blocking requests — each measured against the threshold for a good result, not against other sites. The demo site sits at 87 because six full-resolution images on the homepage add about 1.8 s on a 4G connection. That one issue is most of the gap.
SEO — 20% of the total
Title, meta description, canonical URL, heading structure, robots directives, sitemap coverage, structured data, and whether internal links resolve. This is a technical check, not a ranking prediction — Tenvey has no opinion about your keywords. The demo site loses points for 12 links that point to pages which no longer exist.
Security — 20% of the total
Certificate validity, chain and remaining lifetime; the HTTPS redirect; Strict-Transport-Security, Content-Security-Policy, X-Content-Type-Options and Referrer-Policy; cookie flags; and directory listings or admin endpoints that answer publicly. These are configuration checks read from your own responses — not a penetration test. The demo site scores 97 with one open item: a certificate that expires in six days.
Accessibility — 20% of the total
WCAG 2.2 AA checks against the rendered page: contrast, form labels, alternative text, focus order, landmark structure and heading levels that do not skip. Findings are weighted by how many people they block, so a keyboard trap costs more than a decorative image without alt text. The demo site's newsletter button reaches 2.8:1 where 4.5:1 is required, which is most of the reason it sits at 91.
Uptime — 10% of the total
The share of the last 90 days in which at least two regions received a successful response, and the 5xx responses seen in that window. The demo site is at 99: it stayed up — 99.94% over 90 days — but /checkout returned 500s for part of a day, and those count.
When the score changes
Every category except uptime is recalculated at the next full check, which runs every six hours and within two minutes of a deployment if you send Tenvey a deployment webhook. Fix something and you can run a check by hand rather than wait. Uptime is a rolling 90-day window, so it recovers slowly on purpose: an outage should still be visible in the number a fortnight later.
The total is rounded to the nearest whole number, once, at the end. Category scores are never rounded before they are weighted — that is why 26.1 + 18.8 + 19.4 + 18.2 + 9.9 adds up to 92.4 and not to something a point away from it.
What the score is not
- Not a Lighthouse score. Performance overlaps with Lighthouse's metrics, but it is measured continuously from three regions rather than once in a lab, and the other four categories are Tenvey's own checks.
- Not a compliance statement. 91 on accessibility is not WCAG conformance, and 97 on security is not a security audit. Both are what automated checks can see from outside.
- Not a ranking against other sites. The thresholds are absolute. The comparison worth making is against your own score last week.
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