Developer Guides
Deep-dive guides on i18n formats and frameworks — messages.json, Next.js translations, i18next, and more — written for developers, not translators.
Why Crowdin, Lokalise, and Phrase are overkill for most browser extension projects — and three real alternatives for indie developers who need to translate messages.json without a monthly subscription.
Practical comparison of the three leading Next.js i18n libraries — App Router support, file format, TypeScript safety, pluralization syntax, and when to pick each one.
How the __MSG_key__ substitution syntax works in Chrome and Firefox extension manifests: which fields support it, how Chrome resolves tokens at load time, and the pitfalls that cause silent failures or upload rejections.
How to catch every class of messages.json error before your users do: JSON syntax, missing required fields, missing keys across locales, malformed placeholder syntax, and manifest key mismatches.
Step-by-step guide to adding i18n to a Chrome extension: _locales structure, default_locale, messages.json syntax, chrome.i18n.getMessage(), placeholder preservation, and how to test locale switching.
A complete reference for the WebExtension messages.json format: the message, description, and placeholders fields, $PLACEHOLDER$ syntax, $1 positional substitutions, and common mistakes.
How to set up the _locales folder, what default_locale does in manifest.json, and how Chrome picks the right messages.json at runtime.
Why default_locale is required when _locales exists, what happens when you omit it, and how to fix the most common manifest validation errors.
Using browser.i18n in Firefox add-ons: the messages.json format, AMO localization requirements, and how to avoid common pitfalls on addons.mozilla.org.
How Safari Web Extensions use the same messages.json/_locales format as Chrome and Firefox, and what to know for Mac App Store submission.
The difference between localizing your Chrome Web Store listing and localizing in-extension strings — and the _MSG_ pattern that bridges them.