PranavNagrecha LWC Internationalization
LWC internationalization uses @salesforce/label/c.MyLabel to import translated strings from Custom Labels and @salesforce/i18n/locale + lightning-formatted-* for locale-aware formatting. RTL is supported via the platform's dir attribute; most SLDS styles already mirror correctly. This skill walks through label extraction, locale-aware number/date/currency formatting, pluralization patterns, and RTL audit checklist that together ensure a component works the same for users in every active language and locale without string concatenation pitfalls.
Adoption Signals
Any LWC used in an org with multiple active locales.
- Required when string concatenation, plural forms, or relative-time formatting hard-codes English in the template.
- Required when the layout must support RTL languages (Arabic, Hebrew) — bidirectional CSS is non-trivial.
Recommended Workflow
- Extract every user-visible string into Custom Labels; translate via Translation Workbench.
- Import with
import MY_LABEL from '@salesforce/label/c.MyLabel'. - Format numbers/dates with
<lightning-formatted-number>,<lightning-formatted-date-time>— they honor user locale. - Audit for hard-coded punctuation / date formats (e.g.,
MM/DD/YYYYstring-concat). - Test in at least one LTR + RTL locale (e.g., en-US + he-IL).
Key Considerations
- Custom Labels hold up to 1,000 characters, 5,000 per org (managed-package labels don't count). The often-quoted 255 is a text-field limit, not this one — don't reach for Custom Metadata for a paragraph that fits, because only labels get Translation Workbench.
- Pluralization is not built-in; template a simple singular/plural Custom Label pair.
- Date formatting differences (US vs EU) silently cause misread reports.
- RTL testing reveals icon/chevron directionality bugs.
Worked Examples (see references/examples.md)
- Hardcoded strings audit — New component 'Save' label
- Locale-aware number — Currency display
Common Gotchas (see references/gotchas.md)
- String concat dates — 'MM/DD/YYYY' reads as DD/MM in EU.
- Label over 1,000 chars — Deploy fails.
- RTL icon mirroring — Chevron points wrong way.
Top LLM Anti-Patterns (full list in references/llm-anti-patterns.md)
- Hard-coded English strings
- Concatenating dates/numbers
- Skipping RTL test
Official Sources Used
- Lightning Web Components Developer Guide — https://developer.salesforce.com/docs/platform/lwc/guide/
- Custom Labels (up to 5,000 per org, 1,000 characters each) — https://help.salesforce.com/s/articleView?id=platform.cl_about.htm&type=5
- Lightning Data Service — https://developer.salesforce.com/docs/platform/lwc/guide/data-wire-service-about.html
- LWC Recipes — https://github.com/trailheadapps/lwc-recipes
- SLDS 2 — https://www.lightningdesignsystem.com/2e/