Frankfurter
Frankfurter is a free, open-source, no-API-key-required currency exchange rate API that serves European Central Bank reference rates for 32 currencies with HTTPS and transparent ECB sourcing.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
No authentication is a double-edged sword — zero credential management overhead, but no access control. HTTPS enforced. Open-source codebase is auditable.
⚡ Reliability
Best When
You need ECB reference rates for a small set of major currencies in a prototype, open-source tool, or low-volume internal application where zero cost and zero API key management outweigh the limited currency coverage.
Avoid When
You need more than 32 currencies, production-grade SLAs, or commercial support — use a paid service like Open Exchange Rates or Fixer.io instead.
Use Cases
- • Fetch EUR-based exchange rates for open-source projects or prototypes without any API key management
- • Retrieve historical ECB rates for a specific past date to reconcile financial transactions
- • Build currency conversion tools for side projects or internal tools where free tier limits of paid APIs are a constraint
- • Query time-series rate data over a date range to calculate average exchange rates for a billing period
- • Use as a free fallback data source when a primary paid FX API is unavailable
Not For
- • Applications requiring more than the 32 ECB-tracked currencies — Frankfurter covers far fewer than paid alternatives
- • Commercial production systems where availability guarantees and SLAs are required
- • High-volume automated pipelines that could generate significant load on a free community-operated service
Interface
Authentication
No authentication required. Open API with no key, no signup, and no rate limit documentation. Self-hostable via the open-source repository.
Pricing
Completely free with no tiers. If high availability or rate limits matter, self-host the open-source application.
Agent Metadata
Known Gotchas
- ⚠ Only 32 ECB-tracked currencies are available — requesting an unsupported currency returns a 422 error, not an empty result
- ⚠ Rates update once per ECB business day; do not poll more than once daily or you will receive identical data repeatedly
- ⚠ No SLA or uptime commitment — unsuitable as the sole FX data source for production financial systems
- ⚠ Date range requests for time series use from and to query parameters; the date format must be strict ISO 8601 (YYYY-MM-DD)
- ⚠ The base currency can be changed freely using the from query parameter, unlike free tiers of paid services — a significant advantage for non-EUR workflows
Alternatives
Full Evaluation Report
Comprehensive deep-dive: security analysis, reliability audit, agent experience review, cost modeling, competitive positioning, and improvement roadmap for Frankfurter.
AI-powered analysis · PDF + markdown · Delivered within 30 minutes
Package Brief
Quick verdict, integration guide, cost projections, gotchas with workarounds, and alternatives comparison.
Delivered within 10 minutes
Score Monitoring
Get alerted when this package's AF, security, or reliability scores change significantly. Stay ahead of regressions.
Continuous monitoring
Scores are editorial opinions as of 2026-03-07.