language or language-REGION. Language is ISO 639-1 (two letters, lowercase): en, fr, de, es, zh, ja, ar. Region is ISO 3166-1 alpha-2 (two letters, uppercase): GB, US, DE, FR, CN, JP. Combined with hyphen: en-GB, fr-CA, zh-CN. The 'x-default' special value is the fallback for unmatched locales.

UK is not an ISO 3166-1 country code. The official code for the United Kingdom is GB (Great Britain). Use en-GB. The same trap: cn for Chinese language (correct is zh — cn is a country code for China). The right combinations: zh-CN (Chinese, China), zh-TW (Chinese, Taiwan), zh-HK (Chinese, Hong Kong).

Can I use just the language without region?

Yes. hreflang='en' targets English speakers regardless of country. hreflang='fr' targets French speakers regardless of country. Use language-only when you don't have country-specific variants. Use language-region when you need to differentiate (en-GB vs en-US for UK vs American English spelling).

What about BCP 47 extensions?

BCP 47 allows more complex tags like sr-Latn-RS (Serbian written in Latin script, Serbia) or zh-Hans-CN (Chinese, simplified script, China). Google supports BCP 47 but for most sites the simple language-REGION form is sufficient. Don't over-specify unless you have genuinely script-different variants.

How to Fix Hreflang Language Codes

Hreflang uses ISO 639-1 for language and ISO 3166-1 alpha-2 for region. The wrong codes get silently rejected by Google — your annotation looks fine in source, but Google treats it as missing. Common traps: en-UK (correct is en-GB), cn for Chinese (correct is zh), made-up regional variants. This guide lists the codes, the convention mistakes, and the validation patterns.

1. The format

Hreflang values follow BCP 47 but in practice use one of two shapes:

<!-- Language only -->
<link rel="alternate" hreflang="en" href="/aipageseo-demo-pages/hreflang-fixes-index.html" />
<link rel="alternate" hreflang="fr" href="/aipageseo-demo-pages/hreflang-fixes-index.html" />

<!-- Language + region -->
<link rel="alternate" hreflang="en-GB" href="/aipageseo-demo-pages/hreflang-fixes-index.html" />
<link rel="alternate" hreflang="en-US" href="/aipageseo-demo-pages/hreflang-fixes-index.html" />
<link rel="alternate" hreflang="fr-CA" href="/aipageseo-demo-pages/hreflang-fixes-index.html" />
<link rel="alternate" hreflang="zh-CN" href="/aipageseo-demo-pages/hreflang-fixes-index.html" />

<!-- Special fallback -->
<link rel="alternate" hreflang="x-default" href="/aipageseo-demo-pages/hreflang-fixes-index.html" />

Convention

Language code: lowercase, 2 letters (ISO 639-1)
Region code: uppercase, 2 letters (ISO 3166-1 alpha-2)
Separator: hyphen - (not underscore)
Order: language-REGION (not REGION-language)

2. Common language codes (ISO 639-1)

Language	Code	Common mistake
English	`en`	—
French	`fr`	—
German	`de`	Some use `ge` — wrong
Spanish	`es`	Some use `sp` — wrong
Portuguese	`pt`	—
Italian	`it`	—
Chinese	`zh`	`cn` is a region code, not language
Japanese	`ja`	Some use `jp` — that's region
Korean	`ko`	Some use `kr` — that's region
Arabic	`ar`	—
Russian	`ru`	—
Dutch	`nl`	Some use `du` — wrong
Swedish	`sv`	Some use `se` — that's region
Hebrew	`he`	Some use `iw` (deprecated)
Hindi	`hi`	—
Polish	`pl`	—
Turkish	`tr`	—

3. Common region codes (ISO 3166-1 alpha-2)

Region	Code	Common mistake
United Kingdom	`GB`	`UK` is NOT an ISO code
United States	`US`	—
Germany	`DE`	—
France	`FR`	—
Spain	`ES`	—
Italy	`IT`	—
China	`CN`	—
Japan	`JP`	—
Brazil	`BR`	`br` is also Breton language — case matters in tooling
Canada	`CA`	—
Mexico	`MX`	—
Australia	`AU`	—
India	`IN`	—
Hong Kong	`HK`	—
Taiwan	`TW`	—
Netherlands	`NL`	—

4. Common combined patterns

en          — English, any region
en-GB       — English, United Kingdom (NOT en-UK)
en-US       — English, United States
en-AU       — English, Australia
en-CA       — English, Canada

fr          — French, any region
fr-FR       — French, France
fr-CA       — French, Canada
fr-BE       — French, Belgium
fr-CH       — French, Switzerland

es          — Spanish, any region
es-ES       — Spanish, Spain
es-MX       — Spanish, Mexico
es-AR       — Spanish, Argentina

zh          — Chinese, any region (rarely used alone)
zh-CN       — Chinese, China (simplified)
zh-TW       — Chinese, Taiwan (traditional)
zh-HK       — Chinese, Hong Kong
zh-Hans     — Chinese, simplified script (BCP 47 extension)
zh-Hant     — Chinese, traditional script

pt          — Portuguese
pt-BR       — Portuguese, Brazil
pt-PT       — Portuguese, Portugal

x-default   — Fallback for unmatched locales

5. Validation

Programmatic check

// JavaScript example
const VALID_LANGUAGES = new Set([
  'aa','ab','ae','af','ak','am','an','ar','as','av','ay','az',
  'ba','be','bg','bh','bi','bm','bn','bo','br','bs',
  'ca','ce','ch','co','cr','cs','cu','cv','cy',
  'da','de','dv','dz',
  'ee','el','en','eo','es','et','eu',
  // ... full ISO 639-1 list
]);

const VALID_REGIONS = new Set([
  'AD','AE','AF','AG','AI','AL','AM','AO','AQ','AR','AS','AT','AU','AW','AX','AZ',
  'BA','BB','BD','BE','BF','BG','BH','BI','BJ','BL','BM','BN','BO','BQ','BR','BS',
  // ... full ISO 3166-1 alpha-2 list
]);

function validateHreflang(code) {
  if (code === 'x-default') return true;
  
  const parts = code.split('-');
  if (parts.length === 1) {
    return VALID_LANGUAGES.has(parts[0].toLowerCase());
  }
  if (parts.length === 2) {
    return VALID_LANGUAGES.has(parts[0].toLowerCase()) &&
           VALID_REGIONS.has(parts[1].toUpperCase());
  }
  return false;
}

Node libraries

npm install bcp-47

const { parse } = require('bcp-47');
const result = parse('en-GB');
console.log(result.language);  // 'en'
console.log(result.region);    // 'GB'
// Returns null for invalid tags

6. Common mistakes and fixes

<!-- WRONG: en-UK -->
<link rel="alternate" hreflang="en-UK" href="/aipageseo-demo-pages/hreflang-fixes-index.html" />

<!-- RIGHT: en-GB -->
<link rel="alternate" hreflang="en-GB" href="/aipageseo-demo-pages/hreflang-fixes-index.html" />

<!-- WRONG: cn for Chinese language -->
<link rel="alternate" hreflang="en" href="/aipageseo-demo-pages/hreflang-fixes-index.html" />

<!-- RIGHT: zh for language, optionally zh-CN for China region -->
<link rel="alternate" hreflang="zh-CN" href="/aipageseo-demo-pages/hreflang-fixes-index.html" />

<!-- WRONG: underscore separator -->
<link rel="alternate" hreflang="en_GB" href="/aipageseo-demo-pages/hreflang-fixes-index.html" />

<!-- RIGHT: hyphen -->
<link rel="alternate" hreflang="en-GB" href="/aipageseo-demo-pages/hreflang-fixes-index.html" />

<!-- WRONG: REGION-language order -->
<link rel="alternate" hreflang="GB-en" href="/aipageseo-demo-pages/hreflang-fixes-index.html" />

<!-- RIGHT: language-REGION -->
<link rel="alternate" hreflang="en-GB" href="/aipageseo-demo-pages/hreflang-fixes-index.html" />

7. Verify the fix

Step 1

Re-run Hreflang Checker

Invalid code findings clear. Each annotation parses as valid BCP 47.

Step 2

Search Console International Targeting

Legacy International Targeting report (if accessible) should show no "Incorrect hreflang values" errors.

💡 The most common mistake is en-UK. UK isn't an ISO country code — Great Britain is GB. Almost every site that targets the UK starts with en-UK and silently fails until the audit catches it. Always en-GB.

🌍 Re-run the Hreflang Checker

Verify all language and region codes parse correctly.

Run Hreflang Checker →