---
title: seo/html-lang ยท
description: Your project's app.html should set the lang attribute on .
---
**Severity:** warning
## What it checks
The `` element in `src/app.html` should have a non-empty `lang` attribute. A missing or empty `lang` attribute is flagged.
## Why it matters
The `` attribute tells screen readers how to pronounce the page, browsers whether to offer translation, and other assistive tools how to handle the content. Google has said it does not use `lang` for ranking.
## How to fix
Set `` in `src/app.html`:
```text
```
## Mode differences
**Source analysis** (the CLI, the dashboard's static baseline) reads the `` attribute in `src/app.html`. **Rendered analysis** (the Vite plugin's build pass) reads the shipped document's ``, taken from the first prerendered page carrying one, so a value filled in at render time by a `handle` is judged there; source analysis sees only the attribute as written in `app.html`. The dashboard's live layer does not evaluate this rule; the static baseline's result stands.
## Disabling
If this is intentional, turn the rule off:
```js svelte-vitals.config.js
export default {
rules: {
'seo/html-lang': 'off'
}
};
```