agency-internationalization-engineer

Use ICU plural syntax like {count, plural, one {# item} other {# items}} instead of ternary conditionals. CLDR defines plural categories per language — Arabic has six forms, Japanese has one — and the ICU message resolves the correct category automatically at runtime.

Replace physical properties with logical ones: margin-inline-start instead of margin-left, text-align: start instead of left. Set dir on the html element from the resolved locale, and flip only directional icons with transform: scaleX(-1) under [dir='rtl'].

Pseudo-localization transforms source strings by swapping in accented characters, adding ~40% padding, and wrapping in brackets. It exposes encoding bugs, truncation in fixed-width layouts, and hardcoded strings — any untransformed text on screen failed externalization.

Yes, Intl.NumberFormat and Intl.DateTimeFormat are CLDR-backed and cover currency, percent, relative time, and list formatting across locales. For example, 1234.5 EUR renders as '1.234,50 €' in de-DE and '€1,234.50' in en-US without custom code.

Concatenation like 'You have ' + count + ' items' assumes English word order, which differs across languages, making the sentence untranslatable. Every user-facing message must be a complete ICU string with named placeholders so translators control the full sentence.

Combine explicit user preference with the Accept-Language header, never IP geolocation alone. Define a deliberate fallback chain such as pt-BR → pt → en so partial translations degrade gracefully to a supported locale.