Currency Converter API for JavaScript — Free, No Key Required

Last updated: June 28, 2026 — Read time: 7 min

If you're building a web app and need live exchange rates, most APIs require signup, an API key, or a credit card. Not this one. The Currency Exchange Tool API is completely open — no registration, no auth, CORS enabled. Call it directly from browser JavaScript with fetch().

This guide covers everything you need: a basic converter, error handling, rate-limit awareness, and a complete currency dropdown component.

Try the live API now →

Why This API?

Feature	This API	ExchangeRate-API	Fixer.io
API Key Required	No	Yes	Yes
Signup Required	No	Yes	Yes
CORS Enabled	Yes	No (proxy needed)	No
Currencies	100+	160	170
Monthly Limit	No cap	1,500	100
Rate Updates	Live	Daily	Daily

Quick Start — 3 Lines of JavaScript

const res = await fetch(
  'https://www.currencyexchangetool.com/api/v1/convert?amount=100&from=USD&to=EUR'
);
const data = await res.json();
console.log(`100 USD = ${data.result} EUR at rate ${data.rate}`);

That's it. No headers, no tokens, no SDK. Just a GET request.

Complete Converter Component

Here is a production-ready currency converter component in vanilla JavaScript:

class CurrencyConverter {
  constructor() {
    this.baseUrl = 'https://www.currencyexchangetool.com/api/v1';
  }

  async convert(amount, from, to) {
    if (!amount || amount <= 0) throw new Error('Amount must be positive');
    if (!from || !to) throw new Error('Both currencies are required');

    const url = `${this.baseUrl}/convert?amount=${amount}&from=${from}&to=${to}`;
    
    const res = await fetch(url);
    
    // Check rate-limit headers
    const remaining = res.headers.get('X-RateLimit-Remaining');
    if (remaining === '0') {
      const retryAfter = res.headers.get('Retry-After') || 60;
      throw new Error(`Rate limited. Retry after ${retryAfter} seconds.`);
    }

    if (!res.ok) {
      const err = await res.json();
      throw new Error(err.error || `HTTP ${res.status}`);
    }

    const data = await res.json();
    return {
      from: data.from,
      to: data.to,
      amount: data.amount,
      rate: data.rate,
      result: data.result,
      change24h: data.changePct24h,
      updatedAt: new Date(data.updatedAt),
    };
  }

  async getCurrencies() {
    const res = await fetch(`${this.baseUrl}/currencies`);
    const data = await res.json();
    if (!data.success) throw new Error('Failed to fetch currencies');
    return data.currencies;
  }
}

Usage

const converter = new CurrencyConverter();

// Convert 500 USD to JPY
const result = await converter.convert(500, 'USD', 'JPY');
console.log(`500 USD = ${result.result} JPY (rate: ${result.rate})`);

// Get all available currencies
const currencies = await converter.getCurrencies();
console.log(`${currencies.length} currencies available`);

Building a Currency Selector Dropdown

Use the /api/v1/currencies endpoint to populate a <select> element:

async function populateCurrencySelector(selectElement) {
  const res = await fetch(
    'https://www.currencyexchangetool.com/api/v1/currencies'
  );
  const data = await res.json();
  
  selectElement.innerHTML = '';
  data.currencies.forEach(({ code, name }) => {
    const option = document.createElement('option');
    option.value = code;
    option.textContent = `${code} — ${name}`;
    selectElement.appendChild(option);
  });
}

// Usage
const fromSelect = document.getElementById('fromCurrency');
const toSelect = document.getElementById('toCurrency');
await Promise.all([
  populateCurrencySelector(fromSelect),
  populateCurrencySelector(toSelect),
]);

Error Handling — Complete Pattern

The API returns a structured envelope. Always check success before using the result:

async function safeConvert(amount, from, to) {
  try {
    const res = await fetch(
      `https://www.currencyexchangetool.com/api/v1/convert?amount=${amount}&from=${from}&to=${to}`
    );

    const data = await res.json();

    if (!data.success) {
      // API-level error (unsupported currency, rate not found, etc.)
      console.error(`API error [${data.code}]: ${data.error}`);
      return null;
    }

    return data;
  } catch (err) {
    // Network error or JSON parse failure
    console.error('Network error:', err.message);
    return null;
  }
}

Common Error Codes

HTTP	Code	Meaning
400	`unsupported_currency`	The currency code is not supported
404	—	No rate available for this pair
429	`rate_limited`	Too many requests — check `Retry-After` header
500	—	Internal server error

React Example (useEffect + useState)

import { useState, useEffect } from 'react';

function useExchangeRate(from, to) {
  const [data, setData] = useState(null);
  const [loading, setLoading] = useState(true);

  useEffect(() => {
    let cancelled = false;
    
    async function fetchRate() {
      setLoading(true);
      const res = await fetch(
        `https://www.currencyexchangetool.com/api/v1/convert?amount=1&from=${from}&to=${to}`
      );
      const json = await res.json();
      if (!cancelled) {
        setData(json);
        setLoading(false);
      }
    }

    fetchRate();
    return () => { cancelled = true; };
  }, [from, to]);

  return { data, loading };
}

// Usage
function RateDisplay() {
  const { data, loading } = useExchangeRate('USD', 'UAH');
  if (loading) return <span>Loading...</span>;
  return <span>1 USD = {data.result} UAH</span>;
}

Rate Limiting — Be a Good API Citizen

The API allows 100 requests per minute for convert and currencies endpoints. Every response includes headers to help you stay within limits:

X-RateLimit-Limit — maximum requests per window (100)
X-RateLimit-Remaining — requests left in current window
X-RateLimit-Reset — seconds until the window resets

// Check rate limits before making a request
function checkRateLimit(headers) {
  const remaining = parseInt(headers.get('X-RateLimit-Remaining'));
  if (remaining < 5) {
    console.warn(`Rate limit running low: ${remaining} requests left`);
  }
}

Pro tip: For dashboard or polling use cases, cache the result for 60 seconds instead of calling the API on every render.

Google Sheets Integration

The same API works in Google Sheets with IMPORTXML:

=VALUE(IMPORTXML(
  "https://www.currencyexchangetool.com/api/v1/convert?amount=1&from=USD&to=EUR&format=xml",
  "/response/rate"
))

📖 Read the full API documentation → 💱 Open the free currency converter → 🔓 Why this API is different →