I Built a Free Currency Converter API — No API Key, No Signup

I needed a simple exchange rate API for my currency converter project, but all the popular ones (XE, OANDA, CurrencyLayer, Fixer.io) require signup, an API key, or a credit card. Some cap you at 100 requests per month. Others return data cached yesterday.

So I built my own — and made it completely public.

→ Try it now: currencyexchangetool.com/api-docs

No signup. No API key. No monthly cap. Just make a GET request.

What It Does

The API provides live exchange rates for 100+ currencies, including major, emerging-market, and cross-rate pairs. Rates are fetched live from Yahoo Finance on each request — you always get the current rate, not cached data.

It is rate-limited per IP (not per account): 100 requests/minute for convert and currencies, 30 requests/minute for history. There is no monthly cap and no key to manage.

Endpoints

# Convert 100 USD to EUR
GET /api/v1/convert?from=USD&to=EUR&amount=100

# List supported currencies
GET /api/v1/currencies

# Historical data — last N days, a single date, or a range (max 365 days)
GET /api/v1/history?from=USD&to=UAH&days=7
GET /api/v1/history?from=USD&to=UAH&date=2026-05-01
GET /api/v1/history?from=USD&to=UAH&start_date=2026-04-01&end_date=2026-05-28

Quick Start — cURL

curl -s "https://www.currencyexchangetool.com/api/v1/convert?amount=100&from=USD&to=UAH"

Quick Start — Python

import requests

res = requests.get(
    'https://www.currencyexchangetool.com/api/v1/convert',
    params={'amount': 100, 'from': 'USD', 'to': 'UAH'}
)
data = res.json()
print(f"100 USD = {data['result']} UAH")

Quick Start — JavaScript

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

Quick Start — Go

package main

import (
    "encoding/json"
    "fmt"
    "net/http"
    "net/url"
)

func main() {
    params := url.Values{}
    params.Add("amount", "100")
    params.Add("from", "USD")
    params.Add("to", "UAH")

    resp, _ := http.Get(
        "https://www.currencyexchangetool.com/api/v1/convert?" + params.Encode(),
    )
    defer resp.Body.Close()

    var data map[string]any
    json.NewDecoder(resp.Body).Decode(&data)
    fmt.Printf("100 USD = %v UAH\n", data["result"])
}

Quick Start — PHP

<?php
$response = file_get_contents(
    'https://www.currencyexchangetool.com/api/v1/convert?' .
    http_build_query(['amount' => 100, 'from' => 'USD', 'to' => 'UAH'])
);
$data = json_decode($response, true);
echo "100 USD = {$data['result']} UAH";
?>

Google Sheets — IMPORTXML

Add format=xml for Google Sheets compatibility:

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

How It Compares to Other Free Currency APIs

Key insight: Our API is the only one that combines no API key, no signup, no monthly cap, live rates, and 100+ currencies.

Why "No API Key" Matters

1. Prototyping: No need to stop coding and fill out a registration form
2. Open source: You can commit working examples without exposing API keys
3. CI/CD: No env variables to configure in every pipeline
4. Education: Every student can follow along without their own key
5. Hackathons: Zero setup friction — just write code

Response Format

All endpoints return a consistent JSON envelope (or XML with format=xml):

{
  "success": true,
  "from": "USD",
  "to": "EUR",
  "amount": 100,
  "rate": 0.9234,
  "result": 92.34,
  "change24h": -0.0002,
  "changePct24h": -0.0229,
  "updatedAt": "2026-06-08T12:00:00.000Z"
}

Error responses are predictable:

{
  "success": false,
  "error": "Unsupported currency",
  "code": "unsupported_currency"
}

When you exceed the rate limit you get HTTP 429 with a Retry-After header, and every response carries X-RateLimit-Limit / X-RateLimit-Remaining so you can back off early.

Production Features

• CORS enabled — Access-Control-Allow-Origin: * on every endpoint, with OPTIONS preflight
• Rate limit headers — X-RateLimit-Limit, X-RateLimit-Remaining, X-RateLimit-Reset
• XML output — format=xml for Google Sheets integration
• Historical data — Up to 365 days of daily rates
• SSL/HTTPS — Every request is encrypted

Who This Is For

• Side projects & MVPs — Get building in seconds, not minutes
• E-commerce — Display prices in local currencies
• Fintech dashboards — Live rate widgets without auth complexity
• AI assistants — Simple REST endpoint for currency queries
• Google Sheets users — Pull live rates into spreadsheets
• Students — Learn REST API integration with a no-friction endpoint

Tech Stack

Built with Next.js API routes running on Vercel. No backend database — rates are fetched on-demand from Yahoo Finance. The main site (a currency converter) and the API share the same infrastructure, keeping operational costs near zero.

Give It a Try

The API is live and running right now:

curl -s "https://www.currencyexchangetool.com/api/v1/convert?amount=1&from=USD&to=EUR"

No signup, no API key — it just works.

Documentation: currencyexchangetool.com/api-docs

Main site: currencyexchangetool.com

GitHub: github.com/Kaiukov/currency-converter-vercel

Feedback welcome! Open an issue on GitHub or leave a comment below. If you find this useful, a quick star on GitHub helps others discover it.

More From This Project

• Live EUR/USD Rate — check the current Euro-Dollar rate
• EUR/USD Forecast 2026 — detailed analysis of what's driving the pair
• USD to UAH Converter — real-time US Dollar to Ukrainian Hryvnia rates
• All Currency Pairs — 100+ currencies, instant conversion