---
title: seo/hreflang · hreflang validity
description: hreflang alternates should use valid codes; x-default is recommended for selector/redirect pages.
---
**Severity:** warning
## What it checks
Validates `` alternates. The rule is opt-in: a page with no hreflang alternates is never flagged. When alternates exist it flags:
- a malformed `hreflang` value, meaning neither `x-default` nor a language(-script)(-region) code such as `en`, `en-US`, `zh-Hant`, or `es-419`; and
- a set of two or more alternates with no `x-default` declared.
## Why it matters
A malformed hreflang code breaks international targeting outright. Search engines may serve the wrong language version or ignore the annotations entirely.
A missing `x-default` is a different kind of finding. [Google's own guidance](https://developers.google.com/search/docs/specialty/international/localized-versions) says to "consider adding a fallback page for unmatched languages, especially on language/country selectors or auto-redirecting home pages", a recommendation for that specific shape of page rather than a defect on every multilingual site. A page that lists a fixed set of language alternates without a language selector or auto-redirect has no unmatched-language visitor to fall back for, so skipping `x-default` there is a legitimate choice, not an oversight.
## How to fix
```svelte
```
## Limitations
Validation covers a pragmatic subset of BCP-47, meaning language plus optional script and region, not the full grammar. BCP-47 variants and extensions (e.g. `de-DE-1996`, `en-US-u-hc-h12`) are valid hreflang values but are not recognized here and will be flagged as malformed.
## Mode differences
**Source analysis** (the CLI, the dashboard's static baseline) composes each route's `` from `` in the page and its layout chain, followed into repo-local components, plus the known meta components (`svelte-meta-tags`, `svelte-seo`) and any you declare in `metaComponents`. It judges only a **literal** value; it never examines a dynamic one. **Rendered analysis** (the Vite plugin's build pass, a route you visit in the dashboard) reads the shipped ``, where every value is literal; the build pass covers prerendered routes only. When the two disagree, trust the rendered result.
## Disabling
Record existing findings in the suppressions file (`npx svelte-vitals --update-suppressions`), scope the rule per route or path with `overrides`, or turn it off:
```js svelte-vitals.config.js
export default {
rules: {
'seo/hreflang': 'off'
}
};
```