Svelte i18n Libraries - 2026 Benchmark Report

This page is a benchmark report for i18n solutions on Svelte.

Table of Contents

Interactive Benchmark

Results reference:

See complete benchmark data

See complete benchmark repository here.

Introduction

Internationalisation solutions are among the heaviest dependencies in a Svelte app. The main risk is shipping unnecessary content: translations for other pages and other locales in a single route’s bundle.

As your app grows, that problem can quickly blow up the JavaScript sent to the client and slow down navigation.

In practice, for the least optimised implementations, an internationalised page can end up several times heavier than the version without i18n.

The other impact is on developer experience: how you declare content, types, namespace organisation, dynamic loading, and reactivity when the locale changes.

TL;DR

• Intlayer: The most performance-efficient choice (v8.7.12) with the smallest footprint.
• Paraglide: Strong contender for tree-shaking but has a more complex developer experience and reactivity overhead.
• svelte-i18n: Comprehensive and standard for Svelte, but carries much larger bundle weight (~7× Intlayer).

Test your app

To quickly spot i18n leakage issues, I set up a free scanner available here.

The problem

Two levers are essential to limit the cost of a multilingual app:

• Split content by page / namespace so you do not load whole dictionaries when you do not need them
• Load the right locale dynamically, only when needed

Understanding the technical limitations of these approaches:

Dynamic loading

Without dynamic loading, most solutions keep messages in memory from the first render, which adds significant overhead for apps with many routes and locales.

With dynamic loading, you accept a trade-off: less initial JS, but sometimes an extra request when switching language.

Content splitting

Syntaxes built around t('a.b.c') are very convenient but often encourage keeping large JSON objects at runtime. That model makes tree-shaking hard unless the library offers a real per-page split strategy.

Methodology

For this benchmark, we compared the following libraries:

• Base App (No i18n library)
• svelte-intlayer (v8.7.12)
• svelte-i18n (v4.0.1)
• @inlang/paraglide-js (v2.17.0)

The framework is Svelte with a multilingual app of 10 pages and 10 languages.

We compared four loading strategies:

Strategy summary

• Static: Simple; no network latency after the initial load. Downside: large bundle size.
• Dynamic: Reduces initial weight (lazy-loading). Ideal when you have many locales.
• Scoped static: Keeps code organised (logical separation) without complex extra network requests.
• Scoped dynamic: Best approach for code splitting and performance. Minimises memory by loading only what the current view and active locale need.

GitHub STARs

GitHub stars are a strong indicator of a project's popularity, community trust, and long-term relevance. While not a direct measure of technical quality, they reflect how many developers find the project useful, follow its progress, and are likely to adopt it. For estimating the value of a project, stars help compare traction across alternatives and provide insights into ecosystem growth.

Results in detail

1 - Solutions to avoid

No clear solution to avoid in svelte ecosystem.

2 - Acceptable solutions

(Paraglide) (@inlang/[email protected]):

Paraglide offers an innovative, well-thought-out approach. In the context of a Vite + Svelte app, the tree-shaking their company advertises worked as expected, which is great. But in the case of React + TanStack Start, tree-shaking did not work as expected, same for Next.js. That said, Paraglide's usage in a Svelte and TanStack Start project would be worth a double check. The workflow and DX are also more complex than other options. Personally I am not a fan of having to regenerate JS files before every push, which creates constant merge conflict risk via PRs. The tool also seems more focused on Vite than Next.js. Finally, in comparison with other solutions, Paraglide does not use a store (e.g. Svelte store) to retrieve the current locale to render the content. For each node parsed, it will request the locale from the localStorage / cookie etc. It leads to execution of unnecessary logic that impacts the component reactivity.

Note on paraglide: the solution injects code into your codebase for imports; as a result, the 'lib size' metric in the benchmark report is almost 0. Code generation is a good thing, because the function used will include only the necessary logic (prefix everywhere vs no prefix, cookie vs storage, etc.). In comparison, Intlayer performs this filtering via environment variable injections in the build to force the bundler to tree-shake the content depending on the logic. Thanks to this, paraglide and intlayer end up being 6 to 10 times lighter solutions than i18next or next-intl.

(svelte-i18n) ([email protected]):

This solution answers all i18n needs in a Svelte project. But as it is the case for i18next or other major i18n solutions, it is a bit heavy (~15.9kb, which is about 7× svelte-intlayer).

3 - Recommendations

(Intlayer) ([email protected]):

I will not personally judge svelte-intlayer for objectivity’s sake, since it is my own solution.

Personal note

This note is personal and does not affect the benchmark results. Still, in the i18n world you often see consensus around a pattern like const t = useTranslation('xx') + <>{t('xx.xx')}</> for translated content.

In Svelte apps, injecting a function as a Slot is, in my view, an anti-pattern. It also adds avoidable complexity and JavaScript execution overhead (even if it is barely noticeable).