Technical Definition
ISO 639-1 is the standard for two-letter language codes used in hreflang. Examples: en (English), fr (French), de (German), es (Spanish), ja (Japanese), zh (Chinese). Used with optional ISO 3166-1 alpha-2 region codes for language-region combinations: en-US, en-GB, pt-BR, zh-CN. Required for correct hreflang implementation.
Simple Explanation (ELI13)
ISO language codes are the standard two-letter abbreviations for languages, like 'en' for English, 'fr' for French, and 'de' for German. You use these in hreflang tags. You can also add region codes like 'en-US' for US English or 'en-GB' for British English.
Related Terms
Hreflang, International SEO, Region Codes, Standards
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