ExchangeRate-API 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.
ExchangeRate-API's free tier: 1,500 requests/month, updates once per day. 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.
ExchangeRate-API updates once daily on Free; every 60 minutes on Pro ($10/mo); every 5 minutes on Business ($30/mo). Open Exchange Rates updates hourly on Free/Developer; every 30 minutes on Enterprise ($47/mo); every 5 minutes on Unlimited ($97/mo). ExchangeRate-API sources data from aggregated published sources, per ExchangeRate-API's own documentation. 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, ExchangeRate-API's cheapest paid plan is pro plan, $10/month ($100/year with the annual discount), for 30,000 requests/month with updates every 60 minutes. Open Exchange Rates's cheapest paid plan is developer plan, $12/month, for 10,000 requests/month with hourly updates and all base currencies.
ExchangeRate-API: 1,500 requests/month, updates once per day. Open Exchange Rates: Up to 1,000 requests/month, hourly updates, base currency restricted to USD.
ExchangeRate-API updates once daily on Free; every 60 minutes on Pro ($10/mo); every 5 minutes on Business ($30/mo). 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.
Neither currently does. No MCP integration is listed on ExchangeRate-API's site. No MCP integration is listed on Open Exchange Rates' pricing or signup pages.
ExchangeRate-API's cheapest paid plan is pro plan, $10/month ($100/year with the annual discount), for 30,000 requests/month with updates every 60 minutes. 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 ExchangeRate-API 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 — a capability neither ExchangeRate-API nor Open Exchange Rates currently lists.
Rates are from the free tier, updated intraday on trading days. Indicative only, not for settlement or regulated trading.