Flutter Localization

Keep user-facing text in the project's localization pipeline and model meaning rather than concatenated fragments.

Inspect

Read pubspec.yaml, l10n.yaml, existing ARB files, generated localization access, supported locales, and formatting packages. Preserve the established localization tool unless migration is requested.

Rules

• Use descriptive, stable message keys and document placeholders where translators need context.
• Use ICU plural, select, and placeholder features instead of assembling translated sentences in code.
• Format dates, times, numbers, currencies, and units for the active locale.
• Avoid hardcoded user-facing strings, including errors, semantics labels, and empty states.
• Let directional APIs and start/end alignment support RTL; mirror only assets whose meaning requires it.
• Define a deliberate fallback and unsupported-locale policy.
• Do not infer language from country or persist a locale override the user did not choose.

Verification

Generate localizations, analyze, and test representative locales including an RTL locale, long strings, plurals, missing resources, and locale-aware formats. Run key screens with large text because localization and layout failures often combine.

When formatting messages or localization is in scope, follow the ICU messages and formatting reference.

Sources

• Internationalizing Flutter apps