Frappe Core Translation

Frappe Translation / i18n

> Deterministic patterns for translating Frappe apps across v14, v15, and v16.

Quick Reference

| Task | Python | JavaScript |

|------|--------|------------|

| Translate string | _("Hello") | __("Hello") |

| With substitution | _("Hello {0}").format(name) | __("Hello {0}", [name]) |

| With context | _("Change", context="Coins") | __("Change", null, "Coins") |

| Lazy (module-level) | _lt("Pending") [v15+] | N/A |

| Check RTL | frappe.utils.is_rtl() | frappe.utils.is_rtl() |

Decision Tree

Need to translate a string?
├── In Python (.py)?
│   ├── Inside a function/method → _("text {0}").format(val)
│   ├── Module-level constant [v15+] → _lt("text")
│   └── Module-level constant [v14] → define inside function or use lazy
├── In JavaScript (.js)?
│   └── ALWAYS → __("text {0}", [val])
├── In Jinja template (.html)?
│   └── {{ _("text") }}
├── In Vue (.vue)?
│   └── __("text") in <script>, {{ __("text") }} in <template>
└── DocType label/description/option?
    └── Auto-extracted — no _() needed

Where do translations live?
├── v14 → apps/{app}/{app}/translations/{lang}.csv
├── v15+ → apps/{app}/{app}/locale/{lang}/LC_MESSAGES/{app}.po
└── User overrides → Translation DocType (highest priority)

Need to extract untranslated strings?
├── v14 → bench --site {site} get-untranslated {lang} {output}
└── v15+ → bench generate-pot-file --app {app}

Translation Priority (Highest First)

| Priority | Source | Scope |

|----------|--------|-------|

| 1 | Translation DocType (user overrides) | Per-site |

| 2 | MO files (locale/{lang}/.../{app}.mo) | Per-app [v15+] |

| 3 | CSV files (translations/{lang}.csv) | Per-app |

| 4 | Parent language (e.g., pt for pt-BR) | Fallback |

Version Differences

| Feature | v14 | v15 | v16 |

|---------|-----|-----|-----|

| _() / __() | Yes | Yes | Yes |

| _lt() lazy translation | No | Yes | Yes |

| CSV translations | Yes | Yes (legacy) | Yes (legacy) |

| PO/MO (gettext) | No | Yes | Yes |

| bench generate-pot-file | No | Yes | Yes |

| Babel JS extractor | No | Yes | Yes |

| Type hints on _() | No | No | Yes |

Auto-Extracted Strings (No _() Needed)

These are extracted automatically by the framework:

• DocType labels and descriptions
• Select field options (each option line)
• Workflow states and actions
• Print Format labels
• Report column labels
• Notification subjects (not body)
• Dashboard chart labels

String Extraction Rules

| File Type | Extractor | What It Finds |

|-----------|-----------|---------------|

| .py | Babel (AST) | _("..."), _lt("...") calls |

| .js | Babel tokenizer [v15+] / regex [v14] | __("...") calls |

| .html | Regex | {{ _("...") }} in Jinja |

| .vue | Same as JS | __("...") in script/template |

| .json | DocType parser | Labels, descriptions, options |

CRITICAL: Extractors work on the AST/tokens. They CANNOT extract dynamically constructed strings. See Anti-Patterns.

Anti-Patterns (NEVER Do These)

| Pattern | Why It Breaks | Correct Form |

|---------|---------------|--------------|

| _(f"Hello {name}") | f-string not extractable | _("Hello {0}").format(name) |

| _("Hello " + name) | Concatenation fragments | _("Hello {0}").format(name) |

| _("Welcome %s") % name | Old-style not extractable | _("Welcome {0}").format(name) |

| __(Hello ${name}) | Template literal not extractable | __("Hello {0}", [name]) |

| _(" Hello ") | Leading/trailing spaces trimmed | _("Hello") |

| _("item" if x else "items") | Ternary inside _() | _("item") if x else _("items") |

| _(variable) | Variable not extractable | _("Known String") |

> Full anti-pattern catalog with code examples: references/anti-patterns.md

CSV Translation File Format

Location: apps/{app}/{app}/translations/{lang}.csv

"source","translation","context"
"Hello","Hallo",""
"Change","Wisselgeld","Coins"
"Change","Wijziging","Amendment"

• ALWAYS use UTF-8 encoding (no BOM)
• ALWAYS quote all fields with double quotes
• Context column is optional but MUST be present (empty string if unused)
• No hooks registration needed — auto-discovered from translations/ directory

PO/MO Files [v15+]

Location: apps/{app}/{app}/locale/{lang}/LC_MESSAGES/{app}.po

# Generate POT template
bench generate-pot-file --app {app}

# Migrate existing CSV to PO
bench migrate-csv-to-po --app {app}

# Compile PO to MO (required for runtime)
bench compile-po-to-mo --app {app}

PO files follow standard GNU gettext format. Use any PO editor (Poedit, Weblate, Transifex).

Bench Commands

| Command | Version | Purpose |

|---------|---------|---------|

| bench --site {site} get-untranslated {lang} {output.csv} | All | Export untranslated strings |

| bench update-translations {lang} {untranslated.csv} {translated.csv} | All | Import translations |

| bench generate-pot-file --app {app} | v15+ | Generate .pot template |

| bench migrate-csv-to-po --app {app} | v15+ | Convert CSV to PO format |

| bench compile-po-to-mo --app {app} | v15+ | Compile PO to binary MO |

RTL Support

Hardcoded RTL languages: ar (Arabic), he (Hebrew), fa (Persian/Farsi), ps (Pashto)

# Python
if frappe.utils.is_rtl():
    # Apply RTL-specific logic

// JavaScript
if (frappe.utils.is_rtl()) {
    // Apply RTL-specific logic
}

• Frappe auto-applies dir="rtl" to the <html> element
• ALWAYS use logical CSS properties (margin-inline-start not margin-left) for RTL compatibility
• Bootstrap RTL stylesheet is auto-loaded when RTL language is active

Custom App Translation Workflow

Adding translations to your custom app:

• Write translatable strings using _() / __() with positional placeholders
• Extract untranslated strings:
• v14: bench --site {site} get-untranslated {lang} untranslated.csv
• v15+: bench generate-pot-file --app {app}
• Translate the extracted strings (manually or via PO editor)
• Place translations:
• CSV: apps/{app}/{app}/translations/{lang}.csv
• PO: apps/{app}/{app}/locale/{lang}/LC_MESSAGES/{app}.po
• Compile (v15+ PO only): bench compile-po-to-mo --app {app}
• Clear cache: bench --site {site} clear-cache

Reference Files

| File | Contents |

|------|----------|

| references/api-reference.md | Full Python _() and JS __() API with all signatures and edge cases |

| references/csv-and-bench.md | CSV format spec, bench commands, PO/MO workflow, custom app setup |

| references/anti-patterns.md | Complete anti-pattern catalog with failing and corrected examples |