Internationalisation

Language, locale, direction, and translated content.

• Recommended hreflang for language and regional URLs — hreflang tells search engines which language or regional version of a page to show to which user. It uses BCP 47 codes and must be reciprocal across all alternates.
• Required lang attribute on inline content — Mark passages, phrases, and inline elements that differ from the document language with a lang attribute. WCAG 3.1.2 requires it so assistive tech can switch pronunciation.
• Recommended RTL and bidirectional text — Sites that serve Arabic, Hebrew, Persian, or Urdu must set dir="rtl" and use CSS logical properties so layouts mirror correctly without hard-coded left and right.
• Recommended Locale-aware content — Dates, numbers, currency, and units should be formatted in the user's locale. Use Intl APIs in the browser and the same locale data server-side so output matches expectations.
• Optional Internationalised Domain Names (IDN) — IDNs let domain names contain non-ASCII characters. They are encoded as Punycode on the wire and rendered as Unicode in the browser, subject to anti-spoofing rules.