i18n / Localization
Internationalization (i18n) prepares software for multiple languages. Localization (l10n) adapts content, formats and cultural conventions to a specific target region.
Global markets require software that works in different languages and cultures. Internationalization (i18n) and localization (l10n) are the two disciplines that make this possible. i18n provides the technical foundation – e.g. externalizing text and flexible date formats – while l10n handles the actual translation and cultural adaptation for language, currency, privacy law and conventions. Companies that plan i18n from the start save large costs when expanding into new markets.
What is i18n / Localization?
Internationalization (i18n – 18 letters between 'i' and 'n') is the process of designing and building software so it can be adapted to different languages and regions without code changes. This includes: moving all user-visible text into translation files (e.g. JSON, XLIFF), supporting Unicode/UTF-8 for all scripts, flexible date, number and currency formats, and layouts that handle text expansion (e.g. German ~30% longer than English) and right-to-left languages (Arabic, Hebrew). Localization (l10n) is the subsequent process of actually translating and culturally adapting for a specific market – including images, colours, legal text and regional norms. Both processes overlap and should be planned in parallel.
How does i18n / Localization work?
In practice all visible text is moved into key–value files (e.g. de.json, en.json, fr.json). Frameworks like react-intl, next-intl, vue-i18n or Angular i18n load the right language at runtime based on browser locale or user choice. Pluralization, gender forms and interpolation (e.g. 'Hello {name}') are handled via ICU Message Format or similar. Date and number formatting use the browser Intl API or libraries like date-fns and Luxon. Translation management systems (TMS) like Crowdin, Phrase or Lokalise manage translation workflows with translator access, context screenshots and sync with the code repo.
Practical Examples
Next.js webshop: An online shop uses next-intl with separate JSON files per language and automatic locale detection for DE, EN, FR and ES.
Mobile app with React Native: A travel app uses i18next and react-i18next for 12 languages, including RTL for Arabic and dynamic pluralization.
SaaS dashboard: A B2B tool shows numbers, currencies and dates in the correct format per company location (1,234.56 € vs. $1,234.56).
E-commerce platform: Product descriptions, T&Cs, privacy and checkout are localized per market, including local payment methods.
CMS with multilingual: A headless CMS (Strapi/Contentful) manages content in 8 languages with translation status per article.
Typical Use Cases
Global software launch: New application released in several countries at once
E-commerce expansion: Shop expands into French and Spanish markets with localized product pages
Compliance and law: Legal text (T&Cs, privacy, cookie banner) must be adapted per country
Accessible multilingual: Public and government portals must be multilingual and accessible
Partner portals: B2B platforms serve international partners with their own language and format settings
Advantages and Disadvantages
Advantages
- Market reach: Enter international markets without rebuilding the software
- Cost efficiency: Early i18n architecture avoids expensive retrofits
- User experience: Localized software is perceived as more professional and improves conversion
- SEO: Multilingual content with hreflang improves visibility in international search
- Scalability: New languages can be added without code changes – only new translation files
Disadvantages
- Upfront effort: i18n architecture, externalizing all text and TMS setup take time at project start
- Text expansion: German and French can be 30–40% longer than English – layouts must be flexible
- Translation quality: Machine translation alone is rarely enough – native translators with domain knowledge are needed
- Maintenance: Every new feature must be translated and tested in all languages – effort scales with language count
Frequently Asked Questions about i18n / Localization
What does i18n mean and why the number 18?
When should I start with i18n?
Which tools are there for i18n in React/Next.js?
Related Terms
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