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JSON API

Exchange rate JSON API so simple it barely needs docs

A REST exchange rate API returning plain JSON: every fastFOREX API data point — currencies, crypto, FX pairs and metals — over HTTPS. Any language, any framework, no SDK required, answered in 21 milliseconds on average.

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GET /fetch-one · 200 OK · 4ms
$ curl -H "X-API-Key: YOUR_KEY" \
  "https://api.fastforex.io/fetch-one?from=USD&to=EUR"

{
  "base": "USD",
  "result": {
    "EUR": 0.874883
  },
  "updated": "2026-09-10T09:00:22Z",
  "ms": 4
}

Simple, fast, predictable.

21ms

Average API response time

99.95%

Availability target on every plan

1M

API calls included every month

  • Exchange rates JSON over HTTPS

    No SDK lock-in, no client library to maintain — any HTTP client in any language works. Code samples for JavaScript, Python, PHP, Ruby and Go are in the docs; you can even test endpoints from your browser.

  • Header-based authentication

    Authenticate with the X-API-Key header, keeping keys out of URLs and logs (a query parameter is supported where headers aren't practical). Create separate live, dev and test keys in the Console — rename, rotate or revoke instantly.

  • OpenAPI spec included

    A machine-readable OpenAPI specification covers every endpoint — generate typed clients, import into Postman, or point your AI tooling at it.

    Endpoint docs: OpenAPI spec included

  • Fast by infrastructure

    Served from Google Cloud's Premium Network Tier on global anycast IPv4/IPv6 — traffic rides Google's private backbone and touches the public internet only at the last mile. That's how the average answer takes 21ms.

  • Predictable metering

    One HTTP request equals one API call, whatever it returns (matrix endpoints meter per pair). Track consumption anytime with the /usage endpoint — no surprise bills.

    Endpoint docs: Predictable metering

  • Never-break stability

    Existing endpoints are never changed in breaking ways — evolution ships as new endpoints or versioned paths. Code you write today keeps working.

Build with confidence:

OpenAPI spec (opens in a new tab)Endpoint reference (opens in a new tab)Reliability & SecurityWhere the data comes from

Separate live, dev & test API keys — create, label & manage multiple API keys in the Console

The same API on every plan, from $18/month.

The JSON API is the core of every fastFOREX API plan — One, Extra and Premium all use identical endpoints and authentication. Plans differ only in data speed and depth, never in API mechanics.

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JSON API — FAQ.

The details developers ask about before integrating.

Is there an SDK?
Yes — official SDKs for PHP and Python are on our GitHub, with more languages on the way. You'll never be blocked without one though: the API is plain JSON over HTTPS, the docs carry copy-paste examples for JavaScript, Ruby and Go, and the OpenAPI spec can generate a typed client for any stack.
How do I authenticate?
Send your key in the X-API-Key header — preferred, since it keeps keys out of URLs and server logs. A query-string parameter is also supported for tools that can't set headers.
What's the base URL?
https://api.fastforex.io — HTTPS only; there is no unencrypted endpoint. The API is served on global anycast addresses, so you always reach a nearby edge.
How do I monitor my usage?
Call the /usage endpoint for your current period's start, end, consumption and remaining quota — or check the Console dashboard.
What about rate data over WebSockets or MCP?
Same platform, different delivery: WebSocket streaming pushes live bid/ask without polling, and the MCP Server exposes the API to LLMs and agents. Both sit alongside the JSON API, not instead of it.

Still have questions?

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More from fastFOREX API.

  • Currency API

    Live midpoint rates for 170+ world currencies, answered in 21 milliseconds on average.

    Explore Currency API

  • FX Market Data

    The FX market data API for developers: a live FX rates API with bid/ask quotes on 2,300+ FX trading pairs and OHLC candles down to the minute.

    Explore FX Market Data

  • Crypto API

    A crypto currency exchange API: real-time prices for 500+ crypto making up 750+ pairs, aggregated from the world's biggest exchanges.

    Explore Crypto API

  • Metals API

    A gold price API and precious metals API: real-time spot prices for gold, silver, platinum, palladium and five base metals — priced in any of our 170+ currencies, twelve units of weight and any purity, sourced exclusively from Tier-1 liquidity and delivered over REST and WebSockets.

    Explore Metals API

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