Invalid Hreflang Values

What This Means

One or more hreflang attribute values are not valid BCP 47 language tags. Common invalid values: misspelled language codes, incorrect region codes, incorrect separators (using underscore instead of hyphen), or completely non-standard values.

Why It Matters for SEO

Search engines only recognize correctly formatted BCP 47 language tags. An invalid language code means the hreflang tag is silently ignored — the language targeting for that tag does not take effect. Common examples of invalid values: en_US (underscore instead of hyphen — must be en-US), english (full language name instead of code), en-UK (wrong region code — should be en-GB).

What the Platform Checks

The platform validates each hreflang attribute value against the BCP 47 language tag format. Fires when any tag contains an invalid language code.

How to Fix It

• Use correct BCP 47 format: language code (2-letter ISO 639-1) optionally followed by a hyphen and region code (2-letter ISO 3166-1 alpha-2).
• Valid examples: en, en-US, en-GB, fr, fr-FR, fr-CA, de, zh-Hans, zh-Hant.
• Common fixes: en_US → en-US; en-UK → en-GB; chinese → zh or zh-Hans/zh-Hant.
• Always use x-default for the fallback (not default or en-default).