AI localization for messages.json
Upload your source messages.json, pick target languages, pay once, and download a ready-to-ship _locales ZIP.
How it works
Three simple steps to localize your browser extension. Translations run after payment—we queue jobs and generate the ZIP in minutes.
Upload
Drop your source messages.json file. We parse it instantly and validate the browser extension format.
Select languages & see price
Choose from 52 languages. See transparent pricing based on your file size before you pay.
Download ZIP
Pay once via Stripe. We generate all _locales/{lang}/messages.json files and bundle them into a ZIP.
Transparent pricing estimator
See exactly what you'll pay before uploading. Final quote is computed after upload based on string length and languages selected.
1. Upload file
Drop messages.json here
or click to browse
Chrome, Firefox, Edge, Opera & Safari. Max 500KB.
2. Select languages
3 of 55 languages selected
3. Your estimate
Final price calculated after file upload on checkout page
One-time payment • No subscription
Built for developers
Purpose-built for browser extension locale format. Not a generic translation tool.
WebExtension format aware
Built specifically for browser extension messages.json structure with message, description, and placeholders support.
Placeholder protection
Preserves $PLACEHOLDER$ syntax exactly as-is. Your variables stay intact across all languages.
Description context
We read your description fields and use them as context hints for more accurate AI translations.
ZIP export ready
Download a ZIP with correct _locales/{lang}/messages.json folder structure. Drop it into your extension.
Parallel processing
All languages are translated simultaneously. Most jobs complete in under 5 minutes.
One-time payment
No subscriptions, no monthly fees. Pay once per job, download forever.
How WebExtension extension i18n works
The WebExtension messages.json format is used identically by Chrome, Firefox, Edge, Opera, and Safari. Each key defines a "message" string, an optional "description" that LocalePack uses as translation context, and optional "placeholders" for dynamic values like $USER$. LocalePack generates correct _locales/{locale}/messages.json files for all 5 browsers.
_locales/
├── en/
│ └── messages.json ← default_locale
├── de/
│ └── messages.json
├── fr/
│ └── messages.json
└── ja/
└── messages.json{
"appName": {
"message": "My Extension",
"description": "Extension name"
},
"greeting": {
"message": "Hello, $USER$!",
"placeholders": {
"user": { "content": "$1" }
}
}
}Runtime API
chrome.i18n / browser.i18nExample call
getMessage("key")Required in manifest
"default_locale"Chrome Web Store, AMO, Edge Add-ons, Opera Addons, and Mac App Store all read _locales/ to show localized extension names and descriptions to users in their language.
Why not just use generic tools?
General-purpose translation tools don't understand browser extension format.
LocalePack | Manual translation | Generic TMS | |
|---|---|---|---|
| Setup time | 2 minutes | Hours per language | 30+ minutes |
| Cost transparency | |||
| WebExtension format safety | |||
| Placeholder protection | |||
| Speed (52 languages) | < 5 min | Weeks | Hours |
| Best for | Any WebExtension format | Small projects | Enterprise web apps |
Trusted by extension developers
“Saved me hours of tedious work. Uploaded my messages.json, got back perfect translations in the exact format I needed.”
Sarah K.
Indie dev, AdBlock extension
“Finally a tool that actually understands messages.json format. Placeholders survive translation — no more manual fixes.”
Marcus T.
Extension maintainer
“Transparent pricing was the selling point. I knew exactly what I'd pay before uploading anything.”
Dev J.
Open source contributor
52
Locales supported
100%
Placeholder-safe output
ZIP
Ready to ship
Frequently asked questions
Everything you need to know about LocalePack.