Best Free Currency Exchange Rate API in 2026 (Fiat + Crypto)

Choosing a currency exchange rate API in 2026 comes down to a few things: coverage, data sources, how honest the free tier is, and whether it handles both fiat and crypto. Most APIs are fiat-only — which means a second integration the day you need Bitcoin or a stablecoin. This guide explains what to look for and how CurrencyRest compares.

What to look for in a currency API

• Coverage — fiat and crypto in one place, with cross-rates so any pair is available even if a provider doesn't quote it directly.
• Trustworthy sources — official central-bank rates (ECB, Fed, Bank of England, Bank of Japan) for fiat, real exchanges (Binance, CoinGecko) for crypto, and a transparent fallback when one is down.
• A free tier you can actually build on — not a crippled demo. You should be able to test every currency pair before paying.
• Simple REST + JSON — predictable responses, clear errors (RFC 7807), header-based auth.
• Historical data — for charts, analytics and back-testing.

Why fiat + crypto in one API matters

If your product touches payments, remittances, pricing or portfolios, you will eventually need both. Running two vendors means two SLAs, two billing relationships and two failure modes. A universal API — 108 fiat currencies and 94 cryptocurrencies (202 total) behind one endpoint — removes that tax.

CurrencyRest at a glance

• 202 currencies (fiat + crypto), cross-rates via USD/EUR pivots so any pair resolves.
• 9 data sources with automatic failover and an explicit source selector — you always know where a rate came from.
• Full-access free plan: every currency pair, capped only by volume (300 requests/month). Test with no restrictions before upgrading.
• Live and historical rates, 90-day retention.
• Fast JSON REST, header auth (X-API-Key), RFC 7807 errors, and a real open sandbox on the homepage.

Quick start

Convert 100 USD to XOF (West African CFA franc):

curl "https://api.currencyrest.com/api/v1/convert?from=USD&to=XOF&amount=100" \
  -H "X-API-Key: your_api_key"

{ "from": "USD", "to": "XOF", "amount": 100, "result": 56866.67, "rate": 568.67, "source": "ecb", "timestamp": "..." }

Pin a specific provider with &source=ecb, or omit it to let CurrencyRest pick the best available source and fail over automatically.

Pricing that scales with volume, not features

The free plan already includes every currency and every pair — you only pay when you need more requests. Paid plans start at $9/month (Starter, 15,000 requests) and scale to Pro and Business. There's no "unlock currencies" upsell: the differentiator is volume, not access.

FAQ

Is there a genuinely free currency API? Yes — CurrencyRest's free plan gives full access to all 202 currencies with 300 requests/month, no credit card required.

Does it support crypto? Yes: 94 cryptocurrencies from Binance and CoinGecko, alongside 108 fiat currencies, in the same API.

Where do the rates come from? Central banks (ECB, Fed, BoE, BoJ), market data (TradingView, Google Finance) and crypto exchanges (Binance, CoinGecko), with a Google Search fallback and transparent source selection.

Ready to try it? Create a free API key and make your first call in under a minute.