Frankfurter and Open Exchange Rates 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.
Frankfurter's free tier: Free and unlimited. No API key, signup, or credit card required. Open Exchange Rates's free tier: Up to 1,000 requests/month, hourly updates, base currency restricted to USD. 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.
Frankfurter updates once per business day (ECB reference fix, published around 16:00 CET). No weekend updates. Open Exchange Rates updates hourly on Free/Developer; every 30 minutes on Enterprise ($47/mo); every 5 minutes on Unlimited ($97/mo). Frankfurter sources data from european Central Bank (ECB) reference rates only. Open Exchange Rates sources data from aggregated published sources (banks, financial data providers, and others), per Open Exchange Rates' own documentation.
Once the free tier runs out, Frankfurter's cheapest paid plan is no paid tier exists. The service is entirely free and open source. Open Exchange Rates's cheapest paid plan is developer plan, $12/month, for 10,000 requests/month with hourly updates and all base currencies.
Frankfurter: Free and unlimited. No API key, signup, or credit card required. Open Exchange Rates: Up to 1,000 requests/month, hourly updates, base currency restricted to USD.
Frankfurter updates once per business day (ECB reference fix, published around 16:00 CET). No weekend updates. Open Exchange Rates updates hourly on Free/Developer; every 30 minutes on Enterprise ($47/mo); every 5 minutes on Unlimited ($97/mo). Compare the specific plan you'd actually pay for, not just the headline tier — both vendors gate faster updates behind higher plans.
Yes. Frankfurter runs an official MCP server at mcp.frankfurter.dev, linked from its own homepage. No MCP integration is listed on Open Exchange Rates' pricing or signup pages.
Frankfurter's cheapest paid plan is no paid tier exists. The service is entirely free and open source. Open Exchange Rates's cheapest paid plan is developer plan, $12/month, for 10,000 requests/month with hourly updates and all base currencies. 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 Frankfurter and Open Exchange Rates 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.