Exploring i18n Solutions to Translate Your Svelte Website

As the web continues to connect people across the globe, providing content in multiple languages is increasingly important. For developers working with Svelte, implementing i18n is essential to efficiently manage translations, maintain clean code, and uphold good SEO practices. In this article, we dive into various i18n solutions and workflows for Svelte—helping you choose the one that best suits your project’s needs.

What is Internationalization (i18n)?

Internationalization, commonly abbreviated as i18n, is the process of designing and building your application so it can easily adapt to various languages, regions, and cultural conventions. In Svelte, this typically means setting up translation strings, localizing dates, times, and numbers, and ensuring the user interface can dynamically switch among different locales without major code rewrites.

To learn more about i18n fundamentals, read our article: What is Internationalization (i18n)? Definition and Challenges.

The Translation Challenge for Svelte Applications

Translating a Svelte application can present several hurdles:

• Single-File Components: Svelte’s single-file component approach (where HTML, CSS, and JavaScript exist together) makes it easy for text to become scattered, requiring a strategy to centralise translations.
• Dynamic Content: Data retrieved from APIs or user inputs adds complexity when ensuring content is translated on the fly.
• SEO Considerations: If you’re using SvelteKit for server-side rendering (SSR), configuring localised URLs, meta tags, and sitemaps for effective SEO requires extra care.
• State & Routing: Retaining the correct language across multiple routes and dynamic pages often involves orchestrating global state, route guards, or custom hooks in SvelteKit.
• Maintainability: As your codebase and translation files grow, keeping everything well-organised and synchronised becomes a continuous effort.

Leading i18n Solutions for Svelte

Svelte doesn’t provide a native, built-in i18n solution (as Angular does), but the community has created a variety of robust libraries and patterns. Below are several popular approaches.

1. svelte-i18n

Repository: https://github.com/kaisermann/svelte-i18n

Overview
svelte-i18n is one of the most widely adopted libraries for adding internationalization to Svelte applications. It allows you to dynamically load and switch between locales at runtime and includes helpers for plurals, interpolation, and more.

Key Features

• Runtime Translations: Load translation files on demand, enabling you to switch languages without rebuilding your app.
• Pluralization & Interpolation: Offers a straightforward syntax for handling plural forms and inserting variables within translations.
• Lazy Loading: Only fetch the translation files you need, optimising performance for larger apps or multiple languages.
• SvelteKit Support: Well-documented examples show how to integrate with SSR in SvelteKit for better SEO.

Considerations

• Project Organisation: You’ll need to structure your translation files logically as the project grows.
• SSR Setup: Configuring SSR for SEO might require additional steps to ensure correct locale detection on the server side.
• Performance: While flexible at runtime, a large number of translations loaded at once can impact initial load times—consider lazy loading or caching strategies.

2. svelte-intl-precompile

Repository: https://github.com/cibernox/svelte-intl-precompile

Overview
svelte-intl-precompile uses a precompilation approach to reduce runtime overhead and improve performance. This library integrates the concept of message formatting (similar to FormatJS) while generating precompiled messages at build time.

Key Features

• Precompiled Messages: By compiling translation strings during the build step, runtime performance is improved, and the bundle size can be smaller.
• Integration with SvelteKit: Compatible with SSR, allowing you to serve fully localised pages for better SEO and user experience.
• Message Extraction: Automatically extract strings from your code, reducing the overhead of manual updates.
• Advanced Formatting: Supports pluralization, gender-specific translations, and variable interpolation.

Considerations

• Build Complexity: Setting up precompilation might introduce additional complexity in your build pipeline.
• Dynamic Content: If you need on-the-fly translations for user-generated content, this approach may require extra steps for updates at runtime.
• Learning Curve: The combination of message extraction and precompilation can be slightly more complex for newcomers.

3. i18next with Svelte / SvelteKit

Website: https://www.i18next.com/

Overview
Although i18next is more commonly associated with React or Vue, it’s also possible to integrate it with Svelte or SvelteKit. Leveraging i18next’s broad ecosystem can be helpful if you need consistent i18n across different JavaScript frameworks in your organisation.

Key Features

• Mature Ecosystem: Benefit from an extensive range of plugins, language detection modules, and community support.
• Runtime or Build-Time: Choose between dynamic loading or bundling your translations for slightly faster startup.
• SSR-Friendly: SvelteKit SSR can serve localised content by using i18next on the server side, which is great for SEO.
• Rich Features: Supports interpolation, plurals, nested translations, and more complex i18n scenarios.

Considerations

• Manual Setup: i18next doesn’t have a dedicated Svelte integration out of the box, so you’ll need to configure it yourself.
• Overhead: i18next is robust, but for smaller Svelte projects, some of its features might be overkill.
• Routing & State: Handling language routing will likely involve custom SvelteKit hooks or middlewares.

Final Thoughts

When selecting an i18n strategy for your Svelte app:

1. Assess Project Scale: For smaller projects or quick prototypes, simpler libraries like svelte-i18n or a minimal i18n approach might suffice. Larger, more complex apps may benefit from a typed, precompiled, or more robust ecosystem-based solution.
2. SSO & SSR Considerations: If SEO is critical or you need server-side rendering with SvelteKit, choose a library that supports SSR effectively and can handle localised routes, metadata, and sitemaps.
3. Runtime vs. Build-Time: Decide whether you need dynamic language switching at runtime or prefer precompiled translations for better performance. Each approach involves different trade-offs.
4. TypeScript Integration: If you rely heavily on TypeScript, solutions like Intlayer or libraries with typed keys can significantly reduce runtime errors and improve the developer experience.
5. Maintainability & Scalability: Plan how you’ll organise, update, and version your translation files. Automated extraction, naming conventions, and a consistent folder structure will save time in the long run.

Ultimately, each library offers unique strengths. Your choice depends on performance, developer experience, SEO needs, and long-term maintainability. By selecting a solution that aligns with your project’s goals, you can create a truly global application in Svelte—one that delights users around the world.