Hreflang uses invalid language code — the fix
One or more hreflang annotations use an invalid ISO 639-1 language code or ISO 3166-1 Alpha-2 country code. Google will ignore hreflang entries with unrecognized codes.
Where this fits: indexability in SEO
Indexability is whether a crawled page is allowed into the search index at all. A page can be perfectly reachable and still tell Google to ignore it — through a noindex directive, a conflicting canonical, or an X-Robots-Tag header set by the server. These directives are absolute: one stray meta tag removes a page from search entirely. Indexability issues are the most binary in SEO — the page either can rank or it cannot — which is why they sit at the top of every serious audit.
Why hreflang uses invalid language code hurts your rankings
Invalid language codes cause Google to silently ignore the hreflang annotation, meaning your international targeting will not work for the affected language/region. Common mistakes include using 'uk' for Ukrainian (should be 'uk' for country code but 'uk' is also valid as language), or using three-letter codes instead of two-letter codes.
This is a medium-severity issue: individually modest, but it compounds — dozens of medium issues across hundreds of pages add up to a real quality deficit in how search engines assess the site.
How to fix it
Verify that all hreflang language codes use valid ISO 639-1 two-letter language codes and optionally ISO 3166-1 Alpha-2 country codes. Use format like 'en', 'en-US', 'fr-CA'. Use Google's documentation as a reference for valid codes.
Indexability best practices
- Audit noindex directives after every deploy — one templating mistake can deindex a section overnight.
- Give every indexable page exactly one self-referencing canonical URL.
- Never mix signals: a page should not be canonicalised away AND noindexed AND in the sitemap.
- Use hreflang pairs that reciprocate; a one-way hreflang is ignored.
- Check the HTTP layer too — X-Robots-Tag headers override what you see in the HTML.
The full library: SEO best practices, by category.
Frequently asked questions
What does "Hreflang uses invalid language code" mean?
One or more hreflang annotations use an invalid ISO 639-1 language code or ISO 3166-1 Alpha-2 country code. Google will ignore hreflang entries with unrecognized codes.
Why does hreflang uses invalid language code matter for SEO?
Invalid language codes cause Google to silently ignore the hreflang annotation, meaning your international targeting will not work for the affected language/region. Common mistakes include using 'uk' for Ukrainian (should be 'uk' for country code but 'uk' is also valid as language), or using three-letter codes instead of two-letter codes.
How do I fix hreflang uses invalid language code?
Verify that all hreflang language codes use valid ISO 639-1 two-letter language codes and optionally ISO 3166-1 Alpha-2 country codes. Use format like 'en', 'en-US', 'fr-CA'. Use Google's documentation as a reference for valid codes.
How serious is this issue?
This is a medium-severity issue: individually modest, but it compounds — dozens of medium issues across hundreds of pages add up to a real quality deficit in how search engines assess the site. It belongs to the indexability family of checks.
How do I find every page affected by this on my site?
Run a free Dr Urls audit: it crawls your site, detects hreflang uses invalid language code on every affected page, shows example URLs, and generates a ready-to-use fix task. Re-scan after fixing to verify the issue is gone.
Does your site have this issue?
A free Dr Urls audit crawls your site, finds every page affected by hreflang uses invalid language code, and hands you a ready-made fix task.
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