What does a website SEO audit check?
Seven checks, with a combined weight of 8.5: the Lighthouse SEO score (weight 2), title length (1.5), meta description length (1.5), exactly one H1 (1), a canonical URL (0.75), JSON-LD structured data (1.25) and Open Graph tags (0.5). Titles earn full credit at 30 to 60 characters and meta descriptions at 70 to 160 characters, both taken from Google Search guidance. SEO is the largest category in the rubric by number of checks.
Title and description are scored by range, not by presence. A title inside 30 to 60 characters scores 1.0. Outside the range, credit falls off over a tolerance window of 15 characters, so a 70 character title is 10 characters past the maximum and scores about 0.33, while a 75 character title scores zero. The description window is wider: the tolerance is 45 characters either side of the 70 to 160 range.
Structured data is counted, not just detected. The check reads the JSON-LD @type values found on the page and scores the count divided by 3, capped at 1.0. One type scores 0.33, two score 0.67, three or more score full credit. A page that was fetched and genuinely had no JSON-LD scores zero. A page that was never fetched leaves the check as not measured, which is a different outcome.
The H1 check has three outcomes rather than two: exactly one H1 scores 1.0, zero H1s score 0.0, and two or more score 0.5. Open Graph tags work like structured data, counted and divided by 3 with a cap, so three OG tags is already full credit. The canonical check is the only pure presence test in the category, worth 0.75.
The Lighthouse SEO score is averaged across the mobile and desktop runs when both are available, and taken from whichever single run exists otherwise. SEO carries a weight of 1.15 in the composite score, tied with Performance behind CTA.
What is measured, and how it is scored
7 checks make up the SEO score. Weights are relative within the category and sum to 8.50.
| Check | Rule | Weight |
|---|---|---|
| Lighthouse SEO category score, averaged across the mobile and desktop runs | The 0 to 100 score divided by 100. When both strategies ran, the two scores are averaged first. | 2 |
| Length of the page title | Full credit at 30 to 60 characters. Outside that range credit falls off over a 15 character tolerance window, so 70 characters scores about 0.33 and 75 characters or more scores zero. | 1.5 |
| Length of the meta description | Full credit at 70 to 160 characters. Outside that range credit falls off over a 45 character tolerance window, so a 200 character description scores about 0.11. A page that was read and has no meta description scores zero. A page that was never fetched leaves the check as not measured, which is a different outcome. | 1.5 |
| Number of H1 headings on the page | Exactly one H1 scores 1.0. Zero H1s score 0.0. Two or more score 0.5. | 1 |
| Presence of a canonical URL | Presence only, no threshold. A non-empty canonical scores 1.0, an empty one scores 0.0, and a page that was not inspected leaves the check unscored. | 0.75 |
| Count of JSON-LD @type values found on the page | The count divided by 3, capped at 1.0. Three or more types score full credit, one type scores 0.33. Zero types on a page that was fetched scores 0.0. | 1.25 |
| Count of Open Graph meta tags | The count divided by 3, capped at 1.0. Three or more OG tags score full credit. | 0.5 |
SEO questions
How long should a page title be?+
This audit gives full credit to titles of 30 to 60 characters, which is Google's published guidance. A title of 70 characters scores about 0.33 on the title check, and a title of 75 characters or longer scores zero.
How long should a meta description be?+
70 to 160 characters earns full credit. The taper outside that range is 45 characters wide, so a 180 character description still scores about 0.56 while a 205 character one scores zero.
How much structured data does a page need to pass?+
Three or more distinct JSON-LD @type values earn full credit on the structured data check, because the score is the count divided by three and capped at one. One type scores 0.33 and no structured data at all scores zero.
Is more than one H1 an SEO failure?+
It is a half-credit result, not a failure. The single-H1 check scores 1.0 for exactly one H1, 0.5 for two or more, and 0.0 for none, so missing an H1 entirely costs more than having several.
Does the audit check backlinks or keyword rankings?+
No. Every SEO check reads either the Lighthouse SEO score or the page's own HTML: title, meta description, H1 count, canonical, JSON-LD types and Open Graph tags. Off-page signals such as backlinks and rank positions are not part of the score.
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