Hreflang Syntax Writing Tags Without Errors

Correct syntax, three implementation methods

Hreflang can be implemented in the HTML head as link tags, in the HTTP header (useful for non-HTML files like PDFs), or in an XML sitemap. The link tag format is: link rel="alternate" hreflang="fr-fr" href="https://example.com/fr/". The hreflang value uses ISO 639-1 language code, optionally followed by a hyphen and ISO 3166-1 Alpha-2 country code — language is mandatory, country is optional and must come second, never first.

A frequent error is using region-only codes like hreflang="eu" or reversing the order to "fr-fr" written as country-first "fr-FR" (this specific case is actually fine since fr is language and FR is country, but writing "FR-fr" reversed is invalid). Case doesn't technically matter to Google but convention is lowercase language, uppercase country: fr-FR.

• link rel="alternate" hreflang="en-gb" href="https://example.com/uk/"
• Language code is mandatory; region code is optional and comes second
• Use ISO 639-1 for language, ISO 3166-1 Alpha-2 for region
• Never use continent codes (eu, asia) — they are not valid values
• x-default is written as hreflang="x-default"

The return-tag requirement

Every hreflang relationship must be reciprocal: if page A declares an alternate for page B, page B must declare an alternate back to page A, and both must also self-reference. Google treats one-directional hreflang as invalid and will ignore the entire annotation set for that cluster rather than partially applying it — this is the single biggest cause of hreflang 'not working' complaints.

For large sites, generate all hreflang tags programmatically from a single source of truth (a market/URL mapping table) rather than hand-editing templates per page, since manual editing is where reciprocal tags drift out of sync as pages get added or removed over time.

Key takeaways

• ✓Language code is mandatory, region code is optional and always second
• ✓Every URL in a cluster must self-reference and reciprocate every other URL
• ✓Never use continent codes; only ISO 639-1 and ISO 3166-1 Alpha-2
• ✓Generate hreflang programmatically from a single mapping table at scale

Why this lesson matters

This lesson belongs to Hreflang mastery, the part of International SEO where the goal is: write, validate and maintain hreflang so google serves the correct url to the correct market every time.

Read it once, then do it straight away on a real site inside RankTracker. Nothing here is theory for its own sake — every step produces something you can show a client.

Do it now

1. 1Open RankTracker with sample data already loaded, so you are not stuck on setup.
2. 2Track the keywords from this lesson.
3. 3Use RankTracker's hreflang crawl view to list every hreflang cluster on your site and flag any without matching return tags.