Why it matters
Screen readers pick the wrong pronunciation, browsers offer bogus translation, and search engines have to guess the page language.
How to fix it
Set lang on the root element ().
Example
<html lang="en" suppressHydrationWarning>References
More lint rules
void lint reports 67 rules in this category. Static source checks with no browser: Tailwind v4 silent failures, Next.js 16 API traps, React render-body bugs, accessibility markup, SEO files and motion hygiene.
missing-og-imageNo Open Graph image anywheremissing-iconNo favicon / app iconmissing-llms-txtNo `/llms.txt`dynamic-metadata-streamingRequest-time `generateMetadata` without `htmlLimitedBots`jsonld-missingNo JSON-LD structured datasitemap-lastmod-nowSitemap uses `new Date()` for `lastModified`multiple-h1More than one `<h1>` in a route's page + layoutsjsonld-deprecated-typeJSON-LD type that no longer produces rich results