Fixer

Overview

Fixer (an APILayer product) is one of the most established exchange-rate APIs — rates for 170+ currencies, updated daily, with historical data and conversion on paid tiers. Auth is a free API key.

Note (verified 2026-08): an invalid key returns HTTP 200 with "success": false in the body (APILayer style — check success in the JSON, not the HTTP status).

Quick Start

Latest rates (replace YOUR_KEY):

curl "https://data.fixer.io/api/latest?access_key=YOUR_KEY&symbols=USD,CNY"

{
  "success": true,
  "timestamp": 1724300000,
  "base": "EUR",
  "rates": { "USD": 1.08, "CNY": 7.8 }
}

Historical:

curl "https://data.fixer.io/api/2024-01-01?access_key=YOUR_KEY"

Authentication

• Register at fixer.io → free API key (emailed).
• Send it as the access_key query parameter.
• Invalid keys return 200 + "success": false (verified) — always check the success field.

Rate Limits & Notes

• Free tier: 100 requests/month (EUR base only) — small; paid plans scale.
• Base currency is EUR on the free tier; symbols= trims the response.
• Historical data and other base currencies are paid.
• Responses include a timestamp and rates map.

FAQ

Is Fixer free? Free tier: 100 requests/month; more is paid.

Why does an invalid key return 200? APILayer APIs return "success": false in the body instead of a 4xx — check the JSON.

What’s the base currency on free? EUR — other bases are paid.