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 Chrome extensions
AI localization for Chrome extensions
Upload your source messages.json, pick target languages, pay once, and download a ready-to-ship _locales ZIP.
Placeholder-safe translations
Chrome messages.json compliant
Transparent pricing
How it works
Three simple steps to localize your Chrome extension. 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 Chrome extension 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
Chrome extension 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 Chrome extension locale format. Not a generic translation tool.
Chrome format aware
Built specifically for Chrome 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 Chrome extension i18n works
Chrome extensions declare "default_locale" in manifest.json to enable i18n. The browser then reads locale strings from _locales/{locale}/messages.json at runtime. Each key has a "message" field, an optional "description" for context, and optional "placeholders" for dynamic values — all of which LocalePack understands natively.
_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
chrome.i18nExample call
chrome.i18n.getMessage("appName")Required in manifest
"default_locale"The Chrome Web Store automatically displays your extension name and description in the visitor's locale when _locales/ contains their language folder.
Chrome-specific rules that break builds
Chrome's i18n system fails quietly. These are the four rules that cause most broken releases.
- A fixed list of locale folders
- Chrome reads only a fixed set of locale codes under _locales/. Any folder outside that list is ignored — no build error, no console warning, the strings simply never load.
- Underscores, not hyphens
- Chrome expects pt_BR and zh_CN. BCP-47 style pt-BR or zh-CN does not match any supported locale, so the folder is skipped and the UI falls back to default_locale.
- default_locale is not optional
- If an extension ships a _locales/ directory, manifest.json must declare default_locale. Omit it and the manifest fails validation outright.
- getMessage() is synchronous
- chrome.i18n.getMessage() reads from disk synchronously, which makes it awkward inside an async Manifest V3 service worker — unlike a popup or content script, where it behaves normally.
A key that does not exist returns an empty string and logs nothing at all. Missing translations show up as blank UI, not as errors.
Why not just use generic tools?
General-purpose translation tools don't understand Chrome extension format.
LocalePack | Manual translation | Generic TMS | |
|---|---|---|---|
| Setup time | 2 minutes | Hours per language | 30+ minutes |
| Cost transparency | |||
| Chrome format safety | |||
| Placeholder protection | |||
| Speed (52 languages) | < 5 min | Weeks | Hours |
| Best for | Chrome extensions | 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 Chrome extension 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.
How to localize a Chrome extension (complete guide)
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.
chrome.i18n: the complete API reference
All four chrome.i18n methods with exact signatures and return types: which are synchronous, which return promises, what getMessage() returns when it fails, and how browser.i18n differs in Firefox and Safari.
chrome.i18n in MV3 service workers
Synchronous getMessage() is an advantage in an MV3 service worker, not a problem — a common claim that gets this backwards. What actually breaks is the DOM, global-variable caching, localStorage and XMLHttpRequest.
Best tools for Chrome extension localization
An honest comparison of tools that translate Chrome extension messages.json files: LocalePack, Crowdin, Lokalise, Phrase, POEditor, Localazy, Weblate, and Localeship — setup overhead, pricing models, and placeholder safety.
LocalePack vs Lokalise for Chrome Extensions
Honest comparison of LocalePack and Lokalise for Chrome extension messages.json translation. Lokalise is a full TMS with team workflows and a monthly subscription; LocalePack is upload → pay once → download.