How is the ListSignal SEO score calculated?

Fifteen on-page checks are run against the rendered HTML, each carrying a fixed weight — title (12 points), meta description (10), H1 (10), canonical (8), JSON-LD structured data (10), Open Graph (8), robots noindex (10) and others. When the page was rendered in a real browser, three Core Web Vitals checks are added: LCP, CLS and TTFB. The score is earned points divided by available points, times 100.

Why do some sites have no performance metrics?

LCP and CLS can only be measured by a real browser. Pages fetched over plain HTTP are scored on their 15 content checks alone, and the denominator shrinks accordingly, so a site is never penalised for a measurement that was not taken.

Does ListSignal check for an XML sitemap?

The current score covers on-page signals only. XML sitemap and robots.txt presence are fetched separately at the domain level rather than folded into the page score, because they are site-wide facts rather than properties of a single page.

Methodology

How the SEO score is calculated

A transparent, weighted checklist — not a black box. Every point is attributable, and every failure is named on the record so you can act on it.

The 15 on-page checks

Each check runs against the rendered HTML and carries a fixed weight. The score is earned ÷ available × 100.

Check	Points	Why it matters
Title present	12	The single strongest on-page ranking element. Absent means the page is competing blind.
Title length 10–60	6	Outside this range search results truncate or look thin.
Meta description	10	Controls the snippet. Missing means the engine invents one.
Description length 50–160	5	Too short wastes the slot; too long is cut off.
H1 present	10	Declares the page topic to crawlers and screen readers.
Only one H1	4	Multiple H1s dilute the topic signal.
Canonical tag	8	Prevents duplicate-content splits across parameters and variants.
JSON-LD structured data	10	Required for rich results. Its absence is the most common gap we see.
Open Graph tags	8	Governs how the page renders when shared — a direct traffic lever.
Twitter card	3	Same, for X/Twitter previews.
Viewport meta	6	Without it, mobile rendering is broken and mobile ranking suffers.
html lang attribute	4	Signals language for regional targeting and accessibility.
Image alt coverage ≥ 80%	6	Accessibility plus image-search visibility.
Body content ≥ 300 words	8	Below this, pages rarely rank for anything competitive.
Not noindex	10	A stray noindex removes the page from search entirely — worth catching first.

Core Web Vitals — when we can measure them

LCP and CLS are only observable in a real browser. When a page is rendered by our browser engine, three further checks apply at Google's "good" thresholds: LCP ≤ 2500 ms (10 pts), CLS ≤ 0.1 (5 pts), TTFB ≤ 800 ms (5 pts).

A site is never punished for a measurement we did not take

If a page was fetched over plain HTTP, the performance checks are excluded from both the earned and the available points. That keeps scores comparable instead of quietly penalising pages we simply did not render.

What about XML sitemaps and robots.txt?

Deliberately excluded from the page score. A sitemap is a site-wide fact, not a property of one page, and folding it in would make two pages on the same domain score differently for a reason neither of them controls. We fetch /sitemap.xml and /robots.txt at the domain level and report them as separate flags, which is also how you would want to filter on them.

Why agencies buy this

For SEO agencies — a prospect list that opens itself

Filter for sites with real traffic (Tranco-ranked) that score badly. seo_issues names the exact failures, so your outreach can say "your product pages have no structured data and three of your top templates are missing canonicals" instead of "we noticed some SEO issues". That is the difference between a reply and a delete.

For design and web-build agencies — the redesign trigger

A low score paired with slow LCP and a dated CMS is a site that is costing its owner money right now. Combine with revenue estimation to find the ones that can afford the rebuild, and with hiring signals to find the ones already investing.

For anyone selling to ecommerce

Every score carries its evidence. You can quote a specific, checkable fact in the first line of an email — the single highest-leverage thing in cold outreach.

Other scoring methodology

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