Localization (L10n) for ChatGPT Apps: Regional Customization Guide

Localization (l10n) is critical for ChatGPT apps serving global audiences. Proper localization goes beyond translation—it encompasses cultural adaptation, regional compliance, currency handling, and timezone management. This guide provides production-ready code examples and best practices for building internationally successful ChatGPT applications.

Understanding ChatGPT App Localization

ChatGPT apps reach 800 million weekly users across 180+ countries. Effective localization ensures your app delivers culturally appropriate, legally compliant, and contextually relevant experiences to users worldwide.

Why Localization Matters for ChatGPT Apps

Market Expansion: Apps supporting multiple languages can access 75% more potential users than English-only alternatives.

User Engagement: Localized apps see 3x higher engagement rates in non-English markets compared to machine-translated alternatives.

Regulatory Compliance: Many regions (EU, China, Brazil) require localized content and data handling for legal operation.

Revenue Impact: Properly localized apps generate 2.5x more revenue per user in international markets.

Translation Management System

Building a robust translation management system ensures consistent, maintainable multilingual content across your ChatGPT app.

Translation Manager Implementation

// translation-manager.ts
import { promises as fs } from 'fs';
import path from 'path';

interface TranslationData {
  [key: string]: string | TranslationData;
}

interface LocaleMetadata {
  code: string;
  name: string;
  direction: 'ltr' | 'rtl';
  pluralRules: string;
  dateFormat: string;
  numberFormat: string;
}

class TranslationManager {
  private translations: Map<string, TranslationData> = new Map();
  private localeMetadata: Map<string, LocaleMetadata> = new Map();
  private fallbackLocale: string = 'en';
  private defaultNamespace: string = 'common';

  constructor(fallbackLocale: string = 'en') {
    this.fallbackLocale = fallbackLocale;
  }

  /**
   * Load translations from file system
   */
  async loadTranslations(localesDir: string): Promise<void> {
    const localeFiles = await fs.readdir(localesDir);

    for (const file of localeFiles) {
      if (file.endsWith('.json')) {
        const locale = path.basename(file, '.json');
        const filePath = path.join(localesDir, file);
        const content = await fs.readFile(filePath, 'utf-8');
        const data = JSON.parse(content);

        this.translations.set(locale, data);
      }
    }
  }

  /**
   * Register locale metadata
   */
  registerLocale(metadata: LocaleMetadata): void {
    this.localeMetadata.set(metadata.code, metadata);
  }

  /**
   * Get translated string with fallback support
   */
  translate(
    key: string,
    locale: string,
    params?: Record<string, string | number>,
    namespace: string = this.defaultNamespace
  ): string {
    const fullKey = `${namespace}.${key}`;

    // Try requested locale
    let translation = this.getNestedValue(
      this.translations.get(locale),
      fullKey
    );

    // Fallback to default locale
    if (!translation && locale !== this.fallbackLocale) {
      translation = this.getNestedValue(
        this.translations.get(this.fallbackLocale),
        fullKey
      );
    }

    // Return key if no translation found
    if (!translation) {
      console.warn(`Missing translation: ${fullKey} for locale ${locale}`);
      return key;
    }

    // Interpolate parameters
    if (params) {
      return this.interpolate(translation, params);
    }

    return translation;
  }

  /**
   * Get nested value from translation object
   */
  private getNestedValue(obj: any, path: string): string | null {
    const keys = path.split('.');
    let current = obj;

    for (const key of keys) {
      if (current && typeof current === 'object' && key in current) {
        current = current[key];
      } else {
        return null;
      }
    }

    return typeof current === 'string' ? current : null;
  }

  /**
   * Interpolate parameters into translation string
   */
  private interpolate(
    template: string,
    params: Record<string, string | number>
  ): string {
    return template.replace(/\{\{(\w+)\}\}/g, (match, key) => {
      return key in params ? String(params[key]) : match;
    });
  }

  /**
   * Get locale metadata
   */
  getLocaleMetadata(locale: string): LocaleMetadata | null {
    return this.localeMetadata.get(locale) || null;
  }

  /**
   * Check if locale is RTL
   */
  isRTL(locale: string): boolean {
    const metadata = this.localeMetadata.get(locale);
    return metadata?.direction === 'rtl' || false;
  }
}

export { TranslationManager, LocaleMetadata, TranslationData };

This translation manager provides namespace support, nested key access, parameter interpolation, and fallback handling—essential for maintaining complex multilingual ChatGPT apps.

Cultural Adaptation Engine

Cultural adaptation ensures your ChatGPT app respects regional preferences, customs, and communication styles beyond literal translation.

Cultural Adapter Implementation

// cultural-adapter.ts
interface CulturalPreferences {
  formalityLevel: 'casual' | 'neutral' | 'formal';
  dateFormat: string;
  timeFormat: '12h' | '24h';
  firstDayOfWeek: 0 | 1; // 0 = Sunday, 1 = Monday
  measurementSystem: 'metric' | 'imperial';
  temperatureUnit: 'celsius' | 'fahrenheit';
  currencyPosition: 'before' | 'after';
  decimalSeparator: '.' | ',';
  thousandsSeparator: ',' | '.' | ' ';
}

interface CulturalContext {
  locale: string;
  region: string;
  preferences: CulturalPreferences;
  customRules?: Record<string, any>;
}

class CulturalAdapter {
  private contexts: Map<string, CulturalContext> = new Map();

  /**
   * Register cultural context for a locale
   */
  registerContext(locale: string, context: CulturalContext): void {
    this.contexts.set(locale, context);
  }

  /**
   * Adapt formality level based on cultural norms
   */
  adaptFormality(text: string, locale: string): string {
    const context = this.contexts.get(locale);
    if (!context) return text;

    switch (context.preferences.formalityLevel) {
      case 'formal':
        // Replace casual greetings with formal ones
        return text
          .replace(/\bhey\b/gi, 'Hello')
          .replace(/\bhowdy\b/gi, 'Good day')
          .replace(/\byou\b/gi, 'you') // Could expand to formal "you" in some languages
          .replace(/!/g, '.'); // Reduce exclamation marks

      case 'casual':
        // Make more conversational
        return text
          .replace(/\bGreetings\b/gi, 'Hey')
          .replace(/\bGood day\b/gi, 'Hi there');

      default:
        return text;
    }
  }

  /**
   * Format date according to cultural preferences
   */
  formatDate(date: Date, locale: string): string {
    const context = this.contexts.get(locale);
    if (!context) {
      return date.toLocaleDateString('en-US');
    }

    const format = context.preferences.dateFormat;
    const day = date.getDate().toString().padStart(2, '0');
    const month = (date.getMonth() + 1).toString().padStart(2, '0');
    const year = date.getFullYear();

    return format
      .replace('DD', day)
      .replace('MM', month)
      .replace('YYYY', year.toString())
      .replace('YY', year.toString().slice(-2));
  }

  /**
   * Format time according to cultural preferences
   */
  formatTime(date: Date, locale: string): string {
    const context = this.contexts.get(locale);
    if (!context) {
      return date.toLocaleTimeString('en-US');
    }

    const hours = date.getHours();
    const minutes = date.getMinutes().toString().padStart(2, '0');

    if (context.preferences.timeFormat === '12h') {
      const period = hours >= 12 ? 'PM' : 'AM';
      const displayHours = hours % 12 || 12;
      return `${displayHours}:${minutes} ${period}`;
    } else {
      return `${hours.toString().padStart(2, '0')}:${minutes}`;
    }
  }

  /**
   * Format number according to cultural preferences
   */
  formatNumber(num: number, locale: string): string {
    const context = this.contexts.get(locale);
    if (!context) {
      return num.toLocaleString('en-US');
    }

    const parts = num.toString().split('.');
    const integerPart = parts[0];
    const decimalPart = parts[1];

    // Add thousands separator
    const formatted = integerPart.replace(
      /\B(?=(\d{3})+(?!\d))/g,
      context.preferences.thousandsSeparator
    );

    if (decimalPart) {
      return `${formatted}${context.preferences.decimalSeparator}${decimalPart}`;
    }

    return formatted;
  }

  /**
   * Convert measurements based on regional preferences
   */
  convertMeasurement(
    value: number,
    fromUnit: string,
    locale: string
  ): { value: number; unit: string } {
    const context = this.contexts.get(locale);
    if (!context) {
      return { value, unit: fromUnit };
    }

    const system = context.preferences.measurementSystem;

    // Distance conversions
    if (fromUnit === 'km' && system === 'imperial') {
      return { value: value * 0.621371, unit: 'mi' };
    }
    if (fromUnit === 'mi' && system === 'metric') {
      return { value: value * 1.60934, unit: 'km' };
    }

    // Temperature conversions
    if (fromUnit === 'celsius' && context.preferences.temperatureUnit === 'fahrenheit') {
      return { value: (value * 9/5) + 32, unit: '°F' };
    }
    if (fromUnit === 'fahrenheit' && context.preferences.temperatureUnit === 'celsius') {
      return { value: (value - 32) * 5/9, unit: '°C' };
    }

    return { value, unit: fromUnit };
  }

  /**
   * Get cultural context for locale
   */
  getContext(locale: string): CulturalContext | null {
    return this.contexts.get(locale) || null;
  }
}

export { CulturalAdapter, CulturalPreferences, CulturalContext };

The cultural adapter handles formality levels, date/time formatting, number formatting, and measurement conversions—ensuring your ChatGPT app feels native to users worldwide.

Regional Compliance Checker

Different regions have specific legal requirements for ChatGPT apps. This compliance checker validates your app against regional regulations.

Compliance Checker Implementation

// compliance-checker.ts
interface ComplianceRule {
  id: string;
  region: string;
  regulation: string;
  requirement: string;
  validator: (context: any) => boolean;
  severity: 'error' | 'warning' | 'info';
}

interface ComplianceReport {
  region: string;
  compliant: boolean;
  violations: ComplianceViolation[];
  warnings: ComplianceViolation[];
}

interface ComplianceViolation {
  ruleId: string;
  regulation: string;
  requirement: string;
  severity: 'error' | 'warning' | 'info';
  recommendation: string;
}

class RegionalComplianceChecker {
  private rules: Map<string, ComplianceRule[]> = new Map();

  constructor() {
    this.registerDefaultRules();
  }

  /**
   * Register compliance rules
   */
  private registerDefaultRules(): void {
    // GDPR (EU)
    this.addRule({
      id: 'gdpr-consent',
      region: 'EU',
      regulation: 'GDPR',
      requirement: 'Explicit user consent for data processing',
      validator: (context) => {
        return context.hasConsentMechanism === true &&
               context.consentIsExplicit === true;
      },
      severity: 'error'
    });

    this.addRule({
      id: 'gdpr-data-deletion',
      region: 'EU',
      regulation: 'GDPR',
      requirement: 'Right to deletion (Right to be Forgotten)',
      validator: (context) => {
        return context.hasDeletionEndpoint === true;
      },
      severity: 'error'
    });

    this.addRule({
      id: 'gdpr-data-portability',
      region: 'EU',
      regulation: 'GDPR',
      requirement: 'Data portability in machine-readable format',
      validator: (context) => {
        return context.hasDataExport === true;
      },
      severity: 'error'
    });

    // CCPA (California)
    this.addRule({
      id: 'ccpa-opt-out',
      region: 'US-CA',
      regulation: 'CCPA',
      requirement: 'Do Not Sell My Personal Information',
      validator: (context) => {
        return context.hasOptOutMechanism === true;
      },
      severity: 'error'
    });

    // China Cybersecurity Law
    this.addRule({
      id: 'china-data-localization',
      region: 'CN',
      regulation: 'Cybersecurity Law',
      requirement: 'Data must be stored on servers within China',
      validator: (context) => {
        return context.dataStorageRegion === 'CN';
      },
      severity: 'error'
    });

    // Brazil LGPD
    this.addRule({
      id: 'lgpd-data-protection',
      region: 'BR',
      regulation: 'LGPD',
      requirement: 'Data protection officer (DPO) required',
      validator: (context) => {
        return context.hasDPO === true;
      },
      severity: 'warning'
    });

    // Australia Privacy Act
    this.addRule({
      id: 'aus-privacy-policy',
      region: 'AU',
      regulation: 'Privacy Act',
      requirement: 'Clear privacy policy in plain language',
      validator: (context) => {
        return context.hasPrivacyPolicy === true &&
               context.privacyPolicyLanguage === 'plain';
      },
      severity: 'error'
    });
  }

  /**
   * Add custom compliance rule
   */
  addRule(rule: ComplianceRule): void {
    const regionRules = this.rules.get(rule.region) || [];
    regionRules.push(rule);
    this.rules.set(rule.region, regionRules);
  }

  /**
   * Check compliance for a region
   */
  checkCompliance(region: string, context: any): ComplianceReport {
    const rules = this.rules.get(region) || [];
    const violations: ComplianceViolation[] = [];
    const warnings: ComplianceViolation[] = [];

    for (const rule of rules) {
      const isCompliant = rule.validator(context);

      if (!isCompliant) {
        const violation: ComplianceViolation = {
          ruleId: rule.id,
          regulation: rule.regulation,
          requirement: rule.requirement,
          severity: rule.severity,
          recommendation: this.getRecommendation(rule.id)
        };

        if (rule.severity === 'error') {
          violations.push(violation);
        } else {
          warnings.push(violation);
        }
      }
    }

    return {
      region,
      compliant: violations.length === 0,
      violations,
      warnings
    };
  }

  /**
   * Get recommendation for rule violation
   */
  private getRecommendation(ruleId: string): string {
    const recommendations: Record<string, string> = {
      'gdpr-consent': 'Implement explicit opt-in consent mechanism with clear checkboxes',
      'gdpr-data-deletion': 'Add API endpoint for user data deletion requests',
      'gdpr-data-portability': 'Provide JSON/CSV export functionality for user data',
      'ccpa-opt-out': 'Add "Do Not Sell My Personal Information" link in footer',
      'china-data-localization': 'Deploy app on servers within mainland China',
      'lgpd-data-protection': 'Appoint a Data Protection Officer (DPO)',
      'aus-privacy-policy': 'Simplify privacy policy to 8th-grade reading level'
    };

    return recommendations[ruleId] || 'Consult legal counsel for compliance guidance';
  }

  /**
   * Get all regions with registered rules
   */
  getRegisteredRegions(): string[] {
    return Array.from(this.rules.keys());
  }
}

export { RegionalComplianceChecker, ComplianceReport, ComplianceRule };

This compliance checker validates ChatGPT apps against GDPR, CCPA, China Cybersecurity Law, LGPD, and other regional requirements—critical for legal operation in international markets.

Currency Converter

ChatGPT apps handling payments or pricing need accurate, real-time currency conversion with proper formatting.

Currency Converter Implementation

// currency-converter.ts
interface CurrencyMetadata {
  code: string;
  symbol: string;
  name: string;
  decimalDigits: number;
  symbolPosition: 'before' | 'after';
  thousandsSeparator: string;
  decimalSeparator: string;
}

interface ExchangeRates {
  base: string;
  timestamp: number;
  rates: Record<string, number>;
}

class CurrencyConverter {
  private currencies: Map<string, CurrencyMetadata> = new Map();
  private exchangeRates: ExchangeRates | null = null;
  private cacheTimeout: number = 3600000; // 1 hour

  constructor() {
    this.registerDefaultCurrencies();
  }

  /**
   * Register default currency metadata
   */
  private registerDefaultCurrencies(): void {
    const defaults: CurrencyMetadata[] = [
      { code: 'USD', symbol: '$', name: 'US Dollar', decimalDigits: 2, symbolPosition: 'before', thousandsSeparator: ',', decimalSeparator: '.' },
      { code: 'EUR', symbol: '€', name: 'Euro', decimalDigits: 2, symbolPosition: 'before', thousandsSeparator: '.', decimalSeparator: ',' },
      { code: 'GBP', symbol: '£', name: 'British Pound', decimalDigits: 2, symbolPosition: 'before', thousandsSeparator: ',', decimalSeparator: '.' },
      { code: 'JPY', symbol: '¥', name: 'Japanese Yen', decimalDigits: 0, symbolPosition: 'before', thousandsSeparator: ',', decimalSeparator: '.' },
      { code: 'CNY', symbol: '¥', name: 'Chinese Yuan', decimalDigits: 2, symbolPosition: 'before', thousandsSeparator: ',', decimalSeparator: '.' },
      { code: 'INR', symbol: '₹', name: 'Indian Rupee', decimalDigits: 2, symbolPosition: 'before', thousandsSeparator: ',', decimalSeparator: '.' },
      { code: 'BRL', symbol: 'R$', name: 'Brazilian Real', decimalDigits: 2, symbolPosition: 'before', thousandsSeparator: '.', decimalSeparator: ',' },
      { code: 'CAD', symbol: 'C$', name: 'Canadian Dollar', decimalDigits: 2, symbolPosition: 'before', thousandsSeparator: ',', decimalSeparator: '.' },
      { code: 'AUD', symbol: 'A$', name: 'Australian Dollar', decimalDigits: 2, symbolPosition: 'before', thousandsSeparator: ',', decimalSeparator: '.' }
    ];

    defaults.forEach(currency => {
      this.currencies.set(currency.code, currency);
    });
  }

  /**
   * Load exchange rates from API
   */
  async loadExchangeRates(apiKey: string, baseCurrency: string = 'USD'): Promise<void> {
    try {
      // Example using exchangerate-api.com (replace with your preferred provider)
      const response = await fetch(
        `https://v6.exchangerate-api.com/v6/${apiKey}/latest/${baseCurrency}`
      );

      const data = await response.json();

      if (data.result === 'success') {
        this.exchangeRates = {
          base: baseCurrency,
          timestamp: Date.now(),
          rates: data.conversion_rates
        };
      }
    } catch (error) {
      console.error('Failed to load exchange rates:', error);
      throw new Error('Currency conversion unavailable');
    }
  }

  /**
   * Convert amount between currencies
   */
  convert(amount: number, fromCurrency: string, toCurrency: string): number {
    if (!this.exchangeRates) {
      throw new Error('Exchange rates not loaded');
    }

    // Check if cache is expired
    if (Date.now() - this.exchangeRates.timestamp > this.cacheTimeout) {
      console.warn('Exchange rates cache expired, consider refreshing');
    }

    if (fromCurrency === toCurrency) {
      return amount;
    }

    const fromRate = this.exchangeRates.rates[fromCurrency];
    const toRate = this.exchangeRates.rates[toCurrency];

    if (!fromRate || !toRate) {
      throw new Error(`Unsupported currency: ${!fromRate ? fromCurrency : toCurrency}`);
    }

    // Convert to base currency, then to target currency
    const inBaseCurrency = amount / fromRate;
    return inBaseCurrency * toRate;
  }

  /**
   * Format currency with proper localization
   */
  format(amount: number, currencyCode: string): string {
    const currency = this.currencies.get(currencyCode);
    if (!currency) {
      return `${amount} ${currencyCode}`;
    }

    // Round to appropriate decimal places
    const rounded = amount.toFixed(currency.decimalDigits);
    const parts = rounded.split('.');

    // Add thousands separator
    const integerPart = parts[0].replace(
      /\B(?=(\d{3})+(?!\d))/g,
      currency.thousandsSeparator
    );

    // Combine with decimal part
    const formattedAmount = currency.decimalDigits > 0
      ? `${integerPart}${currency.decimalSeparator}${parts[1]}`
      : integerPart;

    // Add currency symbol
    return currency.symbolPosition === 'before'
      ? `${currency.symbol}${formattedAmount}`
      : `${formattedAmount}${currency.symbol}`;
  }

  /**
   * Get currency metadata
   */
  getCurrencyMetadata(code: string): CurrencyMetadata | null {
    return this.currencies.get(code) || null;
  }
}

export { CurrencyConverter, CurrencyMetadata, ExchangeRates };

This currency converter provides real-time exchange rates, proper number formatting, and symbol positioning—essential for ChatGPT apps with international pricing.

Timezone Handler

ChatGPT apps operating globally need accurate timezone detection, conversion, and display to provide contextually relevant scheduling and time-based features.

Timezone Handler Implementation

// timezone-handler.ts
interface TimezoneInfo {
  identifier: string; // e.g., "America/New_York"
  offset: number; // offset in minutes from UTC
  abbreviation: string; // e.g., "EST"
  isDST: boolean; // Daylight Saving Time active
}

class TimezoneHandler {
  /**
   * Detect user timezone from browser
   */
  static detectTimezone(): string {
    try {
      return Intl.DateTimeFormat().resolvedOptions().timeZone;
    } catch (error) {
      console.warn('Failed to detect timezone, using UTC');
      return 'UTC';
    }
  }

  /**
   * Get timezone info for identifier
   */
  static getTimezoneInfo(identifier: string): TimezoneInfo {
    const now = new Date();
    const formatter = new Intl.DateTimeFormat('en-US', {
      timeZone: identifier,
      timeZoneName: 'short'
    });

    const parts = formatter.formatToParts(now);
    const abbreviation = parts.find(p => p.type === 'timeZoneName')?.value || '';

    // Calculate offset
    const utcDate = new Date(now.toLocaleString('en-US', { timeZone: 'UTC' }));
    const tzDate = new Date(now.toLocaleString('en-US', { timeZone: identifier }));
    const offset = (tzDate.getTime() - utcDate.getTime()) / 60000;

    // Detect DST (simplified)
    const isDST = this.isDaylightSavingTime(now, identifier);

    return {
      identifier,
      offset,
      abbreviation,
      isDST
    };
  }

  /**
   * Convert date between timezones
   */
  static convertTimezone(date: Date, fromTZ: string, toTZ: string): Date {
    const fromString = date.toLocaleString('en-US', { timeZone: fromTZ });
    const toDate = new Date(fromString);

    return new Date(toDate.toLocaleString('en-US', { timeZone: toTZ }));
  }

  /**
   * Format date with timezone
   */
  static formatWithTimezone(
    date: Date,
    timezone: string,
    locale: string = 'en-US',
    options?: Intl.DateTimeFormatOptions
  ): string {
    const defaultOptions: Intl.DateTimeFormatOptions = {
      timeZone: timezone,
      year: 'numeric',
      month: 'short',
      day: 'numeric',
      hour: '2-digit',
      minute: '2-digit',
      timeZoneName: 'short',
      ...options
    };

    return new Intl.DateTimeFormat(locale, defaultOptions).format(date);
  }

  /**
   * Check if date is in Daylight Saving Time
   */
  private static isDaylightSavingTime(date: Date, timezone: string): boolean {
    const jan = new Date(date.getFullYear(), 0, 1);
    const jul = new Date(date.getFullYear(), 6, 1);

    const janOffset = this.getOffset(jan, timezone);
    const julOffset = this.getOffset(jul, timezone);

    const currentOffset = this.getOffset(date, timezone);

    return currentOffset !== Math.max(janOffset, julOffset);
  }

  /**
   * Get UTC offset for date in timezone
   */
  private static getOffset(date: Date, timezone: string): number {
    const utcDate = new Date(date.toLocaleString('en-US', { timeZone: 'UTC' }));
    const tzDate = new Date(date.toLocaleString('en-US', { timeZone: timezone }));
    return (tzDate.getTime() - utcDate.getTime()) / 60000;
  }

  /**
   * Get common timezones by region
   */
  static getTimezonesByRegion(region: string): string[] {
    const timezoneMap: Record<string, string[]> = {
      'North America': [
        'America/New_York',
        'America/Chicago',
        'America/Denver',
        'America/Los_Angeles',
        'America/Toronto',
        'America/Mexico_City'
      ],
      'Europe': [
        'Europe/London',
        'Europe/Paris',
        'Europe/Berlin',
        'Europe/Madrid',
        'Europe/Rome',
        'Europe/Moscow'
      ],
      'Asia': [
        'Asia/Tokyo',
        'Asia/Shanghai',
        'Asia/Hong_Kong',
        'Asia/Singapore',
        'Asia/Dubai',
        'Asia/Kolkata'
      ],
      'Pacific': [
        'Australia/Sydney',
        'Australia/Melbourne',
        'Pacific/Auckland',
        'Pacific/Fiji'
      ],
      'South America': [
        'America/Sao_Paulo',
        'America/Buenos_Aires',
        'America/Santiago'
      ]
    };

    return timezoneMap[region] || [];
  }
}

export { TimezoneHandler, TimezoneInfo };

This timezone handler provides detection, conversion, and formatting capabilities—essential for ChatGPT apps with scheduling, booking, or time-sensitive features.

Integration with ChatGPT Apps

Here's how to integrate these localization components into a ChatGPT app MCP server:

// mcp-server-localized.ts
import { Server } from '@modelcontextprotocol/sdk/server/index.js';
import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js';
import {
  CallToolRequestSchema,
  ListToolsRequestSchema,
} from '@modelcontextprotocol/sdk/types.js';
import { TranslationManager } from './translation-manager.js';
import { CulturalAdapter } from './cultural-adapter.js';
import { CurrencyConverter } from './currency-converter.js';
import { TimezoneHandler } from './timezone-handler.js';

const translationManager = new TranslationManager('en');
const culturalAdapter = new CulturalAdapter();
const currencyConverter = new CurrencyConverter();

// Initialize localization
await translationManager.loadTranslations('./locales');

// Register cultural contexts
culturalAdapter.registerContext('en-US', {
  locale: 'en-US',
  region: 'US',
  preferences: {
    formalityLevel: 'neutral',
    dateFormat: 'MM/DD/YYYY',
    timeFormat: '12h',
    firstDayOfWeek: 0,
    measurementSystem: 'imperial',
    temperatureUnit: 'fahrenheit',
    currencyPosition: 'before',
    decimalSeparator: '.',
    thousandsSeparator: ','
  }
});

culturalAdapter.registerContext('de-DE', {
  locale: 'de-DE',
  region: 'DE',
  preferences: {
    formalityLevel: 'formal',
    dateFormat: 'DD.MM.YYYY',
    timeFormat: '24h',
    firstDayOfWeek: 1,
    measurementSystem: 'metric',
    temperatureUnit: 'celsius',
    currencyPosition: 'after',
    decimalSeparator: ',',
    thousandsSeparator: '.'
  }
});

const server = new Server(
  {
    name: 'localized-chatgpt-app',
    version: '1.0.0',
  },
  {
    capabilities: {
      tools: {},
    },
  }
);

server.setRequestHandler(ListToolsRequestSchema, async () => {
  return {
    tools: [
      {
        name: 'get_localized_content',
        description: 'Get content adapted for user locale',
        inputSchema: {
          type: 'object',
          properties: {
            key: { type: 'string', description: 'Content key' },
            locale: { type: 'string', description: 'User locale (e.g., en-US, de-DE)' },
            params: { type: 'object', description: 'Interpolation parameters' }
          },
          required: ['key', 'locale']
        }
      }
    ]
  };
});

server.setRequestHandler(CallToolRequestSchema, async (request) => {
  if (request.params.name === 'get_localized_content') {
    const { key, locale, params } = request.params.arguments as any;

    const translated = translationManager.translate(key, locale, params);
    const adapted = culturalAdapter.adaptFormality(translated, locale);

    return {
      content: [{ type: 'text', text: adapted }]
    };
  }

  throw new Error('Unknown tool');
});

const transport = new StdioServerTransport();
await server.connect(transport);

Best Practices for ChatGPT App Localization

1. Start with Internationalization (i18n)

Design your ChatGPT app architecture to support localization from day one. Use external translation files, avoid hardcoded strings, and structure your code for multi-language support.

Learn more about ChatGPT app architecture: ChatGPT App Builder Guide

2. Support Right-to-Left (RTL) Languages

For Arabic, Hebrew, and other RTL languages, ensure your UI components properly reverse layout direction while maintaining logical data flow.

Explore ChatGPT app UI components: AI Editor Features

3. Test with Native Speakers

Machine translation catches literal meaning but misses cultural context. Have native speakers review your localized content before launching in new markets.

Deploy globally with confidence: Instant App Wizard

4. Monitor Compliance Changes

Data privacy regulations evolve constantly. Subscribe to legal updates for your target markets and maintain a compliance review schedule.

Understand regional requirements: ChatGPT App Store submission guide

5. Cache Exchange Rates Appropriately

Don't call currency APIs on every request. Cache exchange rates for 1-4 hours depending on your accuracy requirements and API costs.

Optimize ChatGPT app performance: Performance optimization guide

6. Handle Timezone Edge Cases

Be aware of timezone edge cases: DST transitions, countries with multiple timezones (US, Russia, Australia), and half-hour offsets (India, Venezuela).

Build robust ChatGPT apps: Error handling best practices

7. Provide Language Selection

Don't force auto-detection. Allow users to manually select their preferred language and remember their choice across sessions.

Create user-friendly interfaces: ChatGPT App Templates

Common Localization Pitfalls

Hardcoded Strings

Problem: Strings embedded directly in code make translation impossible without code changes.

Solution: Use translation keys: t('welcome.message') instead of "Welcome to our app".

Concatenated Translations

Problem: Building sentences from fragments fails in languages with different grammar rules.

Solution: Use complete sentences with parameter interpolation: t('greeting', { name: userName }).

Date/Time Format Assumptions

Problem: Assuming MM/DD/YYYY format confuses international users.

Solution: Use locale-specific formatters and display timezone explicitly.

Cultural Insensitivity

Problem: Colors, images, or phrases that work in one culture may offend in another.

Solution: Research cultural norms and test with local users before launch.

External resource: W3C Internationalization Best Practices

Localization Testing Checklist

Before deploying your localized ChatGPT app:

• All UI strings use translation keys (no hardcoded text)
• Date/time formats adapt to user locale
• Currency displays correctly (symbol, position, decimal separator)
• RTL languages render correctly (if supported)
• Compliance rules pass for all target regions
• Native speakers have reviewed translations
• Images/icons are culturally appropriate
• Error messages are localized
• Email templates support all languages
• Help documentation exists in all target languages

Deploy your localized app: ChatGPT App Deployment

Build Globally-Ready ChatGPT Apps

Localization transforms ChatGPT apps from English-only tools into global platforms. With proper translation management, cultural adaptation, regional compliance, and technical infrastructure, your app can serve users worldwide while respecting their language, culture, and legal requirements.

Ready to build a globally-ready ChatGPT app? Start your free trial and use our localization templates to reach international markets in hours, not months.

Related Articles:

• ChatGPT App Builder: Complete Guide
• Authentication for ChatGPT Apps
• Performance Optimization for ChatGPT Apps
• Error Handling in ChatGPT Apps
• Security Best Practices for ChatGPT Apps
• Analytics for ChatGPT Apps
• Payment Integration in ChatGPT Apps

External Resources:

• OpenAI Apps SDK Documentation
• W3C Internationalization
• Unicode CLDR