AstrologerAI: an AI astrology app localized into 52 languages
How the AstrologerAI app translated its entire experience into 52 languages with LocalePack — 6.3M tokens for $58.73 — to reach a worldwide audience in their own language.
Purpose-built for Firefox add-ons
AI localization for Firefox add-ons
Upload your source messages.json, pick target languages, pay once, and download a ready-to-ship _locales ZIP.
Placeholder-safe translations
Firefox messages.json compliant
Transparent pricing
How it works
Three simple steps to localize your Firefox add-on. Translations run after payment—we queue jobs and generate the ZIP in minutes.
01
Upload
Drop your source messages.json file. We parse it instantly and validate the Firefox add-on format.
02
Select languages & see price
Choose from 52 languages. See transparent pricing based on your file size before you pay.
03
Download ZIP
Pay once via Stripe. We generate all _locales/{lang}/messages.json files and bundle them into a ZIP.
Live pricing demo
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
Firefox WebExtension format only. Max 500KB.
2. Select languages
|
3 of 55 languages selected
3. Your estimate
Languages selected3
Final price calculated after file upload on checkout page
One-time payment • No subscription
Built for developers
Purpose-built for Firefox add-on locale format. Not a generic translation tool.
Firefox format aware
Built specifically for Firefox add-on 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 Firefox extension i18n works
Firefox WebExtensions use the same messages.json format under _locales/. The "default_locale" field in manifest.json is required whenever the _locales/ directory exists — omitting it causes the add-on to be rejected. The browser.i18n API reads locale strings at runtime, with full support for $PLACEHOLDER$ substitution.
_locales/ folder structure
_locales/
├── en/
│ └── messages.json ← default_locale
├── de/
│ └── messages.json
├── fr/
│ └── messages.json
└── ja/
└── messages.jsonmessages.json
{
"appName": {
"message": "My Extension",
"description": "Extension name"
},
"greeting": {
"message": "Hello, $USER$!",
"placeholders": {
"user": { "content": "$1" }
}
}
}Runtime API
browser.i18nExample call
browser.i18n.getMessage("appName")Required in manifest
"default_locale"AMO (addons.mozilla.org) displays your add-on name and description in the reviewer's locale when _locales/ is present. Consistent translations across all locales improve store approval rates.
Firefox and AMO work differently
Firefox reads the same file format as Chrome, but Mozilla's store handles listing text in a completely separate place.
- Same format, different namespace
- Firefox reads the identical _locales/{locale}/messages.json layout. The runtime namespace is browser.i18n rather than chrome.i18n, with full $PLACEHOLDER$ support.
- default_locale is required
- Whenever the _locales/ directory exists, manifest.json must declare default_locale. Omitting it causes the add-on to be rejected.
- Your AMO listing is a separate job
- The name, summary, and description shown on addons.mozilla.org are not read from _locales/. They are localized separately in the AMO developer hub — Mozilla lets you translate nearly all listing text, including the add-on name.
- Mozilla has no translator pipeline
- Mozilla has publicly acknowledged it has no way to connect extension developers with the translation community at scale, which is why most AMO listings stay English-only.
Shipping a fully localized _locales/ folder does not localize your AMO page. Those are two separate pieces of work.
Why not just use generic tools?
General-purpose translation tools don't understand Firefox add-on format.
LocalePack | Manual translation | Generic TMS | |
|---|---|---|---|
| Setup time | 2 minutes | Hours per language | 30+ minutes |
| Cost transparency | |||
| Firefox format safety | |||
| Placeholder protection | |||
| Speed (52 languages) | < 5 min | Weeks | Hours |
| Best for | Firefox add-ons | Small projects | Enterprise web apps |
Success Cases
Real projects that used LocalePack to reach a global audience in up to 52 languages.
DevToys.pro: 400% international traffic growth across 52 languages
How the DevToys.pro web app translated its entire UI into 52 languages with LocalePack — 5.8M tokens for $58.44 — and quadrupled its international organic traffic.
DevToys New Tab: a Chrome extension localized UI + store listing in 52 languages
How the DevToys New Tab Chrome extension localized both its in-extension UI and its Chrome Web Store listing into 52 languages to reach a global audience.
LocalePack localized itself into 52 languages — with LocalePack
We used our own tool to translate the entire LocalePack site into 52 languages — 2.9M tokens for $27.37 — so developers worldwide find us in their own language.
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 understands Firefox add-on format. No more fixing broken placeholders after translation.”
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.
Related developer guides
Deep dives on the formats, APIs and errors behind this page — written for developers, not translators.
Firefox WebExtensions i18n: messages.json reference
Using browser.i18n in Firefox add-ons: the messages.json format, AMO localization requirements, and how to avoid common pitfalls on addons.mozilla.org.
Localizing your Firefox AMO listing
How to localize an add-on listing on addons.mozilla.org: which fields can be translated, the 250-character summary ceiling and what it costs you in German and Russian, and the per-locale Developer Hub workflow.
messages.json format explained (with placeholders)
A complete reference for the WebExtension messages.json format: the message, description, and placeholders fields, $PLACEHOLDER$ syntax, $1 positional substitutions, and common mistakes.
Chrome extension locale codes: all 55
Every locale code Chrome accepts as a _locales folder name, with language and native names, the underscore-vs-hyphen trap that makes pt-BR silently ignored, and how Chrome picks a locale at runtime.
Browser extension i18n without a TMS subscription
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.