About ICU Playground
Free, browser-based tools for ICU MessageFormat syntax, plural rules, validation, and localization workflows—built for developers, translators, and i18n engineers.
ICU Playground helps you work with ICU MessageFormat—the syntax used by Unicode ICU, many JavaScript i18n stacks, Flutter gen-l10n, and other platforms for pluralization, gender or role selects, ordinal forms, and locale-aware number, date, and time formatting. Our objective is simple: make ICU syntax easier to learn, test, and validate without installing heavyweight tooling.
Whether you are shipping multilingual apps, auditing ARB or JSON resource files, or teaching CLDR plural categories, these utilities stay client-side for quick iteration. We focus on accuracy for standard MessageFormat patterns, clear errors, and references that connect ICU concepts to real localization and internationalization (i18n) tasks.
Official references: ICU MessageFormat (Unicode) · CLDR plural rules.
ICU playground
Edit ICU messages with live preview: plural, select, selectordinal, number, date, and time. Tune variables and locale to see how ICU syntax resolves—ideal for learning MessageFormat and debugging ICU strings.
Open tool →Plural playground
Explore cardinal plural categories (zero, one, two, few, many, other) across locales. Practice ICU plural syntax the way translators and engineers use it with real CLDR-style behavior.
Open tool →Plural rules by locale
Reference which plural forms each locale needs for ICU MessageFormat. Essential for i18n, ICU template design, and matching your source language to target locales.
Open tool →Target template generator
Turn a source ICU message into a target-locale ICU template with the correct plural or ordinal branches—so localization teams can fill every ICU form safely.
Open tool →ICU validator for JSON & ARB
Paste JSON or Flutter ARB files and validate every string as ICU syntax. Catch errors early: malformed braces, missing other clauses, and invalid MessageFormat before ship.
Open tool →Format converters
Reference mappings from ICU plural, select, and selectordinal toward i18next, Android plural strings, and Flutter ARB—handy when migrating between ICU syntax and platform formats.
Open tool →ICU examples library
Copy-paste examples for plural, select, selectordinal, number, date, and time. Speed up onboarding for developers new to ICU MessageFormat and Unicode CLDR conventions.
Open tool →