Fixer and Frankfurter are both REST FX rate APIs. The real differences are free-tier size, update frequency, and where each one starts charging — the table below has the specifics.
Fixer's free tier: 100 API calls/month, hourly updates, base currency restricted to EUR. Frankfurter's free tier: Free and unlimited. No API key, signup, or credit card required. Check both against your expected monthly call volume before committing — a restricted base currency or a low monthly cap can force an upgrade sooner than the sticker price suggests.
Fixer updates hourly on Free/Basic; every 10 minutes on Professional ($59.99/mo); every 60 seconds on Professional Plus ($99.99/mo) and Enterprise. Frankfurter updates once per business day (ECB reference fix, published around 16:00 CET). No weekend updates. Fixer sources data from financial data partners and ECB reference rates, per Fixer's own documentation. Frankfurter sources data from european Central Bank (ECB) reference rates only.
Once the free tier runs out, Fixer's cheapest paid plan is basic plan, $14.99/month, for 10,000 calls/month with hourly updates and all base currencies. Frankfurter's cheapest paid plan is no paid tier exists. The service is entirely free and open source.
Fixer: 100 API calls/month, hourly updates, base currency restricted to EUR. Frankfurter: Free and unlimited. No API key, signup, or credit card required.
Fixer updates hourly on Free/Basic; every 10 minutes on Professional ($59.99/mo); every 60 seconds on Professional Plus ($99.99/mo) and Enterprise. Frankfurter updates once per business day (ECB reference fix, published around 16:00 CET). No weekend updates. Compare the specific plan you'd actually pay for, not just the headline tier — both vendors gate faster updates behind higher plans.
No MCP integration is listed on Fixer's product pages. Yes. Frankfurter runs an official MCP server at mcp.frankfurter.dev, linked from its own homepage.
Fixer's cheapest paid plan is basic plan, $14.99/month, for 10,000 calls/month with hourly updates and all base currencies. Frankfurter's cheapest paid plan is no paid tier exists. The service is entirely free and open source. Compare against your actual monthly call volume, not just the sticker price — overage and rate-limit behavior varies by plan.
If you're choosing between Fixer and Frankfurter mainly on free-tier size or update frequency, exchangerate.dev is worth a look too: a free tier of 10,000 calls/month across 465 pairs, no credit card required, major pairs updating roughly every 60 seconds on trading days, a source and market_session field on every response, and an MCP stdio bridge on every plan including free.
Rates are from the free tier, updated intraday on trading days. Indicative only, not for settlement or regulated trading.