I18n review

i18n Review

The goal: a translator can ship a new locale without touching code, and the result is correct for native speakers, not "English with words swapped."

When to use

• "Review X for i18n / localization"
• "Audit translation readiness"
• "Make this app translatable"
• "Add support for <locale>"

Procedure

1. Identify the framework — i18next, react-intl, vue-i18n, Laravel __(), gettext, Rails I18n, custom? Match existing conventions.
2. Walk the checklist below
3. Group findings by severity

Checklist

String extraction

• No hardcoded user-facing strings in templates, components, or controllers
• Strings live in translation files (en.json, messages.po, lang/en/…)
• Translation keys are stable identifiers, not the English text itself (auth.login.title not "Sign in")
• Keys aren't constructed dynamically (t('errors.' + code) defeats static extraction — use a switch with explicit keys instead)
• No concatenated sentences: t('hello') + ' ' + name → use interpolation: t('hello_name', {name})
• No HTML embedded in translatable strings — use placeholders or rich-text helpers
• Plurals use the framework's plural helper, not if (n === 1)

Plurals

Plural rules vary wildly. English has 2 forms; Polish has 4; Arabic has 6. Don't fake it:

// ❌ Don't
const msg = count === 1 ? '1 item' : `${count} items`;

// ✅ Do
t('item_count', { count })
// en.json: { "item_count_one": "{{count}} item", "item_count_other": "{{count}} items" }
// pl.json: { "item_count_one": "...", "item_count_few": "...", "item_count_many": "...", "item_count_other": "..." }

Dates, numbers, currencies

• No hardcoded date formats (YYYY-MM-DD) for display — use Intl.DateTimeFormat or framework helper
• Numbers formatted with locale separators (1,234.56 vs 1.234,56 vs 1 234,56)
• Currencies formatted with Intl.NumberFormat(locale, {style:'currency', currency}), never by string concat ('$' + amount)
• Currency code stored, locale-formatted on display
• Time zones explicit — store UTC, display in user's TZ
• Week start day not hardcoded (Sunday vs Monday vs Saturday varies)

Text direction (RTL)

• Layout uses logical properties: margin-inline-start not margin-left, padding-inline-end not padding-right
• dir="rtl" flips the layout correctly (test with Arabic, Hebrew, or ?dir=rtl)
• Icons that imply direction (arrows, back/forward) flip in RTL
• Numbers and code blocks stay LTR even in RTL contexts
• No text-align: left when you mean "start" — use text-align: start

Sorting & collation

• Lists sorted with Intl.Collator(locale), not byte-wise / Array.sort()
• Case-insensitive comparisons use localeCompare with proper options
• Search/filter is accent-insensitive where appropriate (sensitivity: 'base')

Input

• Name fields accept unicode (no [a-zA-Z]+ validation)
• Email validation allows internationalized domains
• Phone number format not hardcoded to one country (use libphonenumber or similar)
• Address forms don't assume US-style state/zip
• Long words / long translations don't break layout (German is famously verbose)

Tooling

• Linter / extractor rule prevents new hardcoded strings (eslint-plugin-i18next, i18n-ally, phpcs rules, …)
• CI fails if translations are missing keys (or warns with a baseline)
• Locale fallback chain is explicit (fr-CA → fr → en)
• Language switching doesn't require full reload (where the framework supports it)

Quick greps

# Hardcoded English strings in templates (heuristic)
grep -RInE '>[A-Z][a-z]+ [a-z]+' --include='*.{vue,jsx,tsx,blade.php,erb}' . | head

# Concatenated translations
grep -RInE "t\([^)]+\)\s*\+|i18n\.[a-z]+\([^)]+\)\s*\+" --include='*.{js,ts,jsx,tsx,vue}' .

# Hardcoded currency symbols
grep -RInE "['\"\`]\\\$\{|\\\$[0-9]|'\\\$'" --include='*.{js,ts,jsx,tsx,vue,blade.php}' .

# Physical CSS properties that should be logical
grep -RInE 'margin-(left|right)|padding-(left|right)|text-align:\s*(left|right)' \
  --include='*.{css,scss,vue,jsx,tsx}' .

# Date format strings that look hardcoded
grep -RInE "format\(['\"](YYYY|DD|MM)" --include='*.{js,ts,jsx,tsx,vue}' .

Output format

## i18n review: <scope>

**Framework:** <i18next / vue-i18n / Laravel / …>
**Locales in use:** <en, no, ar, …>

### 🔴 Blockers
- `path/file.tsx:42` — <issue>. **Impact:** <breaks for which locales/users>. **Fix:** <what>.

### 🟠 Major
- …

### 🟡 Minor
- …

### ✅ What's working
- <category> — <one sentence>

Severity rubric

Tag	Meaning
🔴 Blocker	Cannot be translated correctly (hardcoded strings, broken plurals, broken RTL layout)
🟠 Major	Renders incorrectly for many locales (date/number format, sorting, address forms)
🟡 Minor	Polish (long-text overflow, missing locale fallback)

Anti-patterns

• ❌ t('You have ' + count + ' messages') — broken in every language with grammatical agreement
• ❌ Translating button text but baking in width: 80px (German "Einstellungen" doesn't fit)
• ❌ Storing formatted currency in DB ("$10.00")
• ❌ Sorting names with Array.sort() instead of Intl.Collator
• ❌ Right-aligned designs that "just work" in LTR
• ❌ Assuming names have a first and a last name with a space between
• ❌ Validating names with [a-zA-Z\s]+
• ❌ Mirror-flipping all icons in RTL (don't flip clocks, logos, media controls)

Useful references

• Unicode CLDR — locale data the world relies on
• W3C Internationalization Activity — specs and guides
• MDN: Intl — browser-native locale APIs
• Falsehoods Programmers Believe About Names
• Falsehoods Programmers Believe About Time