Fixer.io
Fixer.io is a currency exchange rate API backed by European Central Bank data, providing real-time and historical rates for 168 currencies with EUR as the default base, operated by APILayer.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
HTTP-only on the free tier is a serious security deficiency; the API key in query parameter pattern risks exposure in server logs. HTTPS only available on paid plans.
⚡ Reliability
Best When
Building a European application or working with Euro-centric financial data where ECB reference rates are the natural and trusted source, and you want a low-cost hosted API over fetching ECB data directly.
Avoid When
You need USD as your base currency without paying for a plan upgrade, or you need more than 168 currencies (Open Exchange Rates covers more).
Use Cases
- • Convert Euro-denominated prices to other currencies for European e-commerce storefronts
- • Fetch daily ECB reference rates for compliance reporting or financial audit trails
- • Build historical FX rate lookups for accounting systems that need to reconcile transactions at the rate in effect on the transaction date
- • Display live currency conversion in a travel or expense management application
- • Calculate cross-rates between non-EUR currency pairs using the EUR base as the pivot
Not For
- • Applications requiring a non-EUR base currency on the free tier — base currency switching requires paid plans
- • High-frequency or algorithmic trading requiring sub-second rate updates
- • Official regulatory submissions requiring a certified or audited rate source
Interface
Authentication
API access key passed as a query parameter (access_key). Free tier requires HTTP (not HTTPS) — HTTPS is a paid feature, which is a significant security concern for production use.
Pricing
The free tier's HTTP-only restriction makes it unsuitable for production; HTTPS requires at minimum the Basic paid plan. APILayer product family.
Agent Metadata
Known Gotchas
- ⚠ Free tier uses HTTP not HTTPS — never use the free tier in production as API keys will be transmitted in plaintext
- ⚠ Base currency is locked to EUR on the free and Basic plans; changing the base requires Professional plan or manual cross-rate calculation
- ⚠ ECB rates are updated once per business day — do not poll more frequently than daily or you waste quota without gaining fresher data
- ⚠ The access_key appears in the URL query string — avoid logging raw request URLs to prevent key exposure
- ⚠ Weekends and ECB holidays produce no rate updates; the API returns the last available rate without clearly flagging that it is stale
Alternatives
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Scores are editorial opinions as of 2026-03-07.