5 Free Exchange Rate APIs With No API Key Required (2026)

If you're prototyping a checkout flow, a remittance tool, a travel app, or a quick personal-finance script, the last thing you want to do is sign up for an account, hand over a credit card, and rotate an API key — just to convert USD to EUR.

This is a real comparison of 5 exchange rate APIs that you can hit right now, with zero registration, from a fresh terminal. I tested every endpoint on the day of writing (2026-05-16); every code sample below ran successfully against the actual service.

TL;DR — pick by use case:

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Why "no API key" matters

People search for "no API key" not because they don't understand authentication — they understand it perfectly well. They want one of three things:

1. Speed of prototyping — a hackathon, a sketch, a one-off script. You'll measure the API in seconds-to-first-response, not in monthly invoice.
2. Avoiding key-rotation overhead — if you don't have a secret, you can't leak it, you can't accidentally commit it, and you don't need a vault.
3. Avoiding lock-in to a commercial vendor — most "free" APIs that require a key gate the good stuff behind a paid tier and quietly track your traffic.

For low-volume reads of public, daily-updated data like exchange rates, no-key is a perfectly defensible production choice. The "use a paid commercial API" answer kicks in when you need sub-minute updates, SLAs, or commercial guarantees — and we'll cover that threshold at the end.

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1. open.er-api.com — the simplest possible answer

ExchangeRate-API runs a no-key endpoint at open.er-api.com. It's the closest thing to "what most people actually need."

curl https://open.er-api.com/v6/latest/USD

Response (truncated):

{
  "result": "success",
  "base_code": "USD",
  "time_last_update_utc": "Sat, 16 May 2026 00:02:31 +0000",
  "rates": {
    "EUR": 0.859854,
    "JPY": 158.55,
    "CNY": 6.8106,
    "GBP": 0.7401,
    "...": "..."
  }
}

Best for: any app where USD is your home base and "yesterday's rate" is fresh enough. Watch out: you must pin USD as base. If your home base is EUR/CNY/etc., you'll either need to derive rates client-side (rate[X] / rate[Y]) or use a different API.

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2. Frankfurter — historical data and ECB rates, no key

Frankfurter (now at api.frankfurter.dev — the older api.frankfurter.app returns a 301 redirect) is built around the European Central Bank reference rates and is the only no-key option here with a real historical endpoint.

# Latest
curl 'https://api.frankfurter.dev/v1/latest?base=USD&symbols=EUR,JPY,CNY'

# Historical (any date back to 1999)
curl 'https://api.frankfurter.dev/v1/2024-01-02?base=USD&symbols=EUR'

# Time series
curl 'https://api.frankfurter.dev/v1/2026-01-01..2026-05-16?base=USD&symbols=EUR'

Response from the latest endpoint:

{
  "amount": 1.0,
  "base": "USD",
  "date": "2026-05-15",
  "rates": { "CNY": 6.8106, "EUR": 0.85999, "JPY": 158.55 }
}

Best for: any app that needs charts, backfills, or "show me USD/EUR on the day I bought it." Watch out: only 30-ish currencies (the major liquid pairs). No exotic crosses, no crypto.

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3. Fawazahmed0 currency-api — widest coverage via CDN

This one is structurally different from the rest: it's not a hosted API, it's a daily-updated static JSON dataset served from the jsdelivr CDN. Which means: no rate limit, edge-cached globally, and 341 currencies including crypto.

# All USD pairs (~341 currencies)
curl https://cdn.jsdelivr.net/npm/@fawazahmed0/currency-api@latest/v1/currencies/usd.json

# Single pair (USD → EUR)
curl https://cdn.jsdelivr.net/npm/@fawazahmed0/currency-api@latest/v1/currencies/usd/eur.json

# Specific date
curl https://cdn.jsdelivr.net/npm/@fawazahmed0/currency-api@2024-01-02/v1/currencies/usd.json

Response:

{
  "date": "2026-05-16",
  "usd": {
    "eur": 0.86023046,
    "cny": 6.80859036,
    "jpy": 158.62,
    "btc": 0.0000172,
    "...": "..."
  }
}

Best for: apps that need exotic currencies, crypto-fiat conversions, or zero-latency edge delivery. Watch out: it's a community-maintained dataset. Mission-critical compliance use cases should use an official source. The repo lives on GitHub — give it a star.

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4. European Central Bank XML feed — straight from the source

If you want the canonical, central-bank-issued reference rate with no intermediary, the ECB publishes a daily XML file at a stable URL that's been alive for two decades:

curl https://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml

Response (excerpt):

<Cube>
  <Cube time='2026-05-16'>
    <Cube currency='USD' rate='1.1628'/>
    <Cube currency='JPY' rate='184.36'/>
    <Cube currency='GBP' rate='0.87050'/>
    <Cube currency='CNY' rate='8.0210'/>
  </Cube>
</Cube>

Best for: any app where you want the most institutionally-credible source, or where you're already in the Eurozone and don't need a USD base. Watch out: XML, not JSON — you'll parse with xml2js, lxml, etc. EUR-only base.

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5. Bank of Canada Valet — official Canadian rates

If you're building anything Canada-centric, the Bank of Canada exposes a clean, no-key REST API called Valet. It's the canonical source for CAD pairs.

# Latest USD/CAD observation
curl 'https://www.bankofcanada.ca/valet/observations/FXUSDCAD/json?recent=1'

# Last 30 days
curl 'https://www.bankofcanada.ca/valet/observations/FXUSDCAD/json?recent=30'

Response:

{
  "observations": [
    { "d": "2026-05-15", "FXUSDCAD": { "v": "1.3752" } }
  ]
}

Best for: Canadian fintech, anything where you need a regulator-grade CAD source. Watch out: Each currency pair is a separate series. You request one pair at a time.

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When to outgrow the free tier

The honest threshold:

• Updates more frequent than daily → you need a commercial feed (e.g., Open Exchange Rates paid, ExchangeRate-API paid, Frankfurter has no realtime). Daily is the bound on every API in this list.
• SLAs or signed agreements → commercial vendor or self-hosted snapshot of a paid feed.
• More than ~100k requests/day → check Terms of Use. Most of these will tolerate it for legitimate apps but it's polite to cache aggressively at your edge.
• Anything regulated (FX trading, broker-dealer use, AML) → use a regulator-approved source. The free APIs above are reference data, not transactional data.

For 95% of side-project, internal-tool, and small-SaaS use cases, you'll never cross that line.

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Recap — pick your default

All five are still alive, free, and key-less as of May 2026 — every code sample above was tested against the live endpoint.

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Related on XScanHub:

• ExchangeRate-API detail page
• Developer Tools category