Reference

Supported Languages

langctl works with any language you can identify with a standard language code, and stores all text as Unicode. This reference lists common languages and their codes.

Language Codes

langctl uses BCP 47 language codes: a lowercase ISO 639 language code (en, fil), optionally followed by a region (ISO 3166-1, e.g. pt-BR) or a script (e.g. zh-Hans).

Format

• Base language: en (English)
• Regional variant: en-US (English - United States), en-GB (English - United Kingdom)
• Script variant: zh-Hans (Chinese - Simplified), zh-Hant (Chinese - Traditional)

Commonly Used Languages

The most popular languages for international applications:

European Languages

Western Europe

Central & Eastern Europe

Asian Languages

East Asia

Southeast Asia

South Asia

West Asia & Middle East

Using Languages in langctl

Adding Languages to a Project

Via Dashboard

1. Select the project in the sidebar
2. Open Languages
3. Click Add Language
4. Search for the language and select it

The dashboard offers a list of common languages (the base codes such as en, es, pt, zh). To add other codes, including regional and script variants like pt-BR or zh-Hant, use the CLI.

The number of languages per project depends on your plan: 3 on Free, 10 on Starter, unlimited on Pro and above.

Via CLI

langctl projects add-language my-project ja

langctl projects add-language my-project ja ko zh

langctl projects add-language my-project en-US en-GB pt-BR

The default language is the source language for translations and AI translation, and the language langctl push uploads by default:

langctl projects create "My App" \
--default-language en \
--languages en,es,fr,de

langctl projects update my-app --default-language en

AI Translation Coverage

AI translation uses DeepL, which supports many but not all languages. If DeepL can’t translate between two languages, langctl shows an error naming the pair; you can still add those translations by hand, by import or from the CLI.

Use regional variants for locale-specific differences:

langctl projects create "Mobile App" \
--languages en,zh-Hans,zh-Hant

langctl keys create mobile-app home.welcome \
--value en="Welcome" \
--value zh-Hans="欢迎" \
--value zh-Hant="歡迎"

Languages that read right-to-left:

• Arabic (ar)
• Hebrew (he)
• Persian/Farsi (fa)
• Urdu (ur)

/* CSS automatically applied for RTL languages */
[dir="rtl"] {
text-align: right;
direction: rtl;
}

langctl supports full Unicode (UTF-8):

• Latin scripts: Basic Latin, Latin Extended
• Cyrillic: Russian, Ukrainian, Bulgarian
• CJK: Chinese, Japanese, Korean
• Arabic: Arabic, Persian, Urdu
• Indic: Devanagari, Bengali, Tamil, Telugu
• Other: Greek, Hebrew, Thai, Georgian

Track translation progress per language:

langctl projects stats my-project

projects stats shows key counts and, for each language, how many keys are translated. In CI, langctl pull --require-complete exits with an error if any language is missing translations.

Begin with 2-3 languages and expand:

--languages en,es

langctl projects add-language my-app fr de it

langctl projects add-language my-app ja zh ko

Only add variants when there are significant differences:

--languages en-US,en-GB,pt-BR,pt-PT

--languages es-ES,es-MX,es-AR,es-CO  # Start with just es

Add languages based on your user base:

1. Analyze user location data
2. Add top 3-5 language markets first
3. Ensure 100% completion before adding more
4. Expand gradually based on growth

--languages en,es,pt,fr,de,ja,zh

--languages en,de,fr,es,it,pl,nl

--languages en,zh-Hans,ja,ko,th,vi,id

Check that translations exist:

langctl projects stats my-project     # translated/total per language
langctl keys get my-project home.welcome  # all translations of one key
langctl pull --require-complete          # fail if any language is incomplete

Ensure UTF-8 encoding:

<!-- HTML -->
<meta charset="UTF-8">

<!-- iOS Strings file -->
// Save with UTF-8 encoding

<!-- Android XML -->
<?xml version="1.0" encoding="utf-8"?>

Next Steps

• Export Formats - Format-specific requirements
• Web Integration - Framework setup
• Mobile Integration - iOS and Android
• Subscription & Usage - Language limits by plan