Paraglide JS

Overview

Paraglide JS is a compiler-based i18n library that generates typed message functions and runtime helpers. Use this skill when a project needs Paraglide setup, message usage, locale detection, SSR integration, or refactoring around generated paraglide/ output.

When To Use

• Adding Paraglide JS to a new or existing app
• Updating locale strategy order or custom strategies
• Wiring SSR locale detection with paraglideMiddleware()
• Integrating Paraglide into TanStack Start
• Reusing one project.inlang across a monorepo

Do not use this skill for generic copywriting or translation quality review. It is for code integration and runtime behavior.

Core Workflow

1. Identify the app shape: Vite app, SSR app, TanStack Start app, or monorepo.
2. Prefer the Vite plugin for Vite-based apps.
3. Use CLI compilation when bundler integration is unavailable or when a package needs explicit compile scripts.
4. Add server middleware only for SSR/server request flows.
5. Keep project.inlang and message files as the source of truth; treat generated paraglide/ output as build artifacts.
6. Recompile after changing messages, locales, strategy, or output settings.

Rules Of Thumb

• Prefer paraglideVitePlugin() in Vite projects instead of hand-rolling generated output.
• Prefer built-in strategies before adding custom ones.
• Order strategies intentionally. Earlier strategies win.
• Use one owner for URL rewriting. Do not combine router-level URL rewrites and middleware-driven URL localization without checking for redirect loops.
• In monorepos, default to "each package compiles" unless every consumer can share one identical strategy/runtime.

Reference Guide

• Read [references/basics.md](./references/basics.md) for setup, generated files, and message/runtime usage.
• Read [references/strategies.md](./references/strategies.md) for strategy ordering and custom strategies.
• Read [references/tanstack-start.md](./references/tanstack-start.md) for TanStack Start integration patterns.
• Read [references/monorepo.md](./references/monorepo.md) for shared project.inlang patterns across packages.

Common Mistakes

• Editing generated src/paraglide/* files directly instead of changing source messages or config
• Forgetting to recompile after changing messages/*.json or project.inlang/settings.json
• Adding paraglideMiddleware() to client-only SPAs
• Putting a preference strategy before url without expecting redirect behavior
• Using TanStack Router rewrites and URL-based middleware localization together without testing for loops

External Sources

• Official docs: https://inlang.com/m/gerre34r/library-inlang-paraglideJs/
• Vite guide: https://inlang.com/m/gerre34r/library-inlang-paraglideJs/vite
• Monorepo guide: https://inlang.com/m/gerre34r/library-inlang-paraglideJs/monorepo
• Middleware guide: https://inlang.com/m/gerre34r/library-inlang-paraglideJs/middleware
• TanStack Router i18n guide: https://tanstack.com/router/v1/docs/framework/react/guide/internationalization-i18n