--- title: SEO description: Every SEO rule svelte-vitals runs. --- {/* rules-index:start */} Resolved <head> metadata, structured data, and crawlability: what search engines actually see. | Rule | Severity | Summary | | ------------------------------------------------------------------- | ----------- | -------------------------------------------------------------------------------------------------------- | | [`seo/title-presence`](/rules/seo/title-presence) | 🔴 critical | Every route should resolve a non-empty <title>. | | [`seo/canonical-url`](/rules/seo/canonical-url) | 🟡 warning | Every route should include a <link rel="canonical"> tag. | | [`seo/charset`](/rules/seo/charset) | 🟡 warning | The page should declare a character encoding with <meta charset>. | | [`seo/description-presence`](/rules/seo/description-presence) | 🟡 warning | Every route should include a <meta name="description">. | | [`seo/duplicate-description`](/rules/seo/duplicate-description) | 🟡 warning | Each route should have a unique meta description. | | [`seo/duplicate-title`](/rules/seo/duplicate-title) | 🟡 warning | Each route should have a unique <title>. | | [`seo/hreflang`](/rules/seo/hreflang) | 🟡 warning | hreflang alternates should use valid codes; x-default is recommended for selector/redirect pages. | | [`seo/html-lang`](/rules/seo/html-lang) | 🟡 warning | Your project's app.html should set the lang attribute on <html>. | | [`seo/image-alt`](/rules/seo/image-alt) | 🟡 warning | Every <img> should have an alt attribute. | | [`seo/json-ld-relative-url`](/rules/seo/json-ld-relative-url) | 🟡 warning | URLs in JSON-LD should be absolute. | | [`seo/json-ld-required-props`](/rules/seo/json-ld-required-props) | 🟡 warning | A recognized @type should include the properties its rich result requires. | | [`seo/json-ld-validity`](/rules/seo/json-ld-validity) | 🟡 warning | A page's JSON-LD must be valid JSON with @context and @type. | | [`seo/og-image`](/rules/seo/og-image) | 🟡 warning | Every route should include a <meta property="og:image"> tag. | | [`seo/og-title`](/rules/seo/og-title) | 🟡 warning | Every route should include a <meta property="og:title"> tag. | | [`seo/og-url`](/rules/seo/og-url) | 🟡 warning | Every route should include an og:url with its canonical address. | | [`seo/robots-txt`](/rules/seo/robots-txt) | 🟡 warning | Your project should provide a robots.txt file. | | [`seo/single-h1`](/rules/seo/single-h1) | 🟡 warning | Each page should have exactly one <h1>. | | [`seo/sitemap-xml`](/rules/seo/sitemap-xml) | 🟡 warning | Your project should provide a sitemap.xml file. | | [`seo/ssr-disabled`](/rules/seo/ssr-disabled) | 🟡 warning | export const ssr = false makes a route's content invisible to non-JS crawlers and slower to first paint. | | [`seo/viewport`](/rules/seo/viewport) | 🟡 warning | Pages should declare a responsive viewport meta tag. | | [`seo/description-length`](/rules/seo/description-length) | 🔵 info | The meta description should be 70–160 characters. | | [`seo/heading-level-skip`](/rules/seo/heading-level-skip) | 🔵 info | Heading levels should not be skipped. | | [`seo/indexability`](/rules/seo/indexability) | 🔵 info | A route should not be accidentally set to noindex. | | [`seo/json-ld`](/rules/seo/json-ld) | 🔵 info | Every route should include JSON-LD structured data. | | [`seo/json-ld-date-format`](/rules/seo/json-ld-date-format) | 🔵 info | Date properties in JSON-LD should be ISO-8601. | | [`seo/json-ld-deprecated-type`](/rules/seo/json-ld-deprecated-type) | 🔵 info | Some schema types had their Google rich result dropped or restricted. | | [`seo/json-ld-placeholder`](/rules/seo/json-ld-placeholder) | 🔵 info | JSON-LD should not contain unreplaced placeholder text. | | [`seo/og-description`](/rules/seo/og-description) | 🔵 info | Every route should include an og:description. | | [`seo/sitemap-in-robots`](/rules/seo/sitemap-in-robots) | 🔵 info | robots.txt should point crawlers at your sitemap. | | [`seo/title-length`](/rules/seo/title-length) | 🔵 info | The document title should be 30–60 characters. | | [`seo/twitter-card`](/rules/seo/twitter-card) | 🔵 info | Pages should declare a twitter:card for rich sharing on X/Twitter. | {/* rules-index:end */} See [Configuration](/guides/configuration) to change a rule's severity or turn it off.