Frankfurter

Frankfurter is a free and open-source currency data API that tracks reference exchange rates published by central banks.

The API is publicly available at https://api.frankfurter.dev.

Deployment

Using Docker

docker run -d -p 8080:8080 \
  -e FRED_API_KEY=your_key \
  -e TCMB_API_KEY=your_key \
  --pull always \
  lineofflight/frankfurter

Both API keys are optional. The app runs without them.

• FRED_API_KEY enables Federal Reserve (FRED) data. Register at fred.stlouisfed.org for a free key.
• TCMB_API_KEY enables Turkish Central Bank data. Register at evds3.tcmb.gov.tr for a free key.

Data is fetched asynchronously on startup, so some endpoints may return empty results briefly until the initial backfill completes. To avoid this, you can mount a volume to persist data across container restarts:

docker run -d -p 8080:8080 \
  -e DATABASE_URL=sqlite:///app/data/frankfurter.sqlite3 \
  -v ./data:/app/data \
  --pull always \
  lineofflight/frankfurter

One-Click Deploy

Cloud Provider	Deploy Button
AWS
DigitalOcean
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Libraries / Tools

• beancount-exchangerates: a Beancount price source plugin using this API
• frankfurte-rs: Rust library and CLI to interface with this API

Contributing

Frankfurter is built with Ruby. To contribute:

1. Fork.
2. Install dependencies with bundle install.
3. Run tests with APP_ENV=test bundle exec rake.
4. Push your changes to a feature branch.
5. Open a pull request.

Roadmap

• Migrate to SQLite
• Add API versioning in path
• Multiple data providers (ECB, BOC, TCMB)
• v2 API with normalized response format
• Deploy as a blockchain oracle