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-startnotmargin-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 |