Open source alternative to Open Exchange Rates, Fixer, CurrencyAPI, Currencylayer and Exchange Rates API
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Serve exchange rate data for 219 currencies from 111 central banks, with daily history back to 1948 and no API key required.
Frankfurter provides accurate daily mid-market reference rates for invoice generation, revenue reporting, and financial analytics. The historical feed goes back to 1948, covering any period a finance team is likely to query.
Skip if your billing system needs real-time rates updated faster than once per day, or if your pricing requires bid/ask spreads rather than mid-market references.
Fetch rates once daily and cache them locally to show prices in a visitor's currency without per-request API fees. Frankfurter explicitly encourages storing daily observations locally for caching and analytics, keeping API traffic light.
Skip if you are in a jurisdiction where import pricing requires the central bank's official declared rate on the transaction date, and that rate is not among Frankfurter's 111 sources.
The daily history back to 1948 and the time-series endpoint with grouping by week or month make it straightforward to analyze decades of monetary history. NDJSON streaming keeps memory usage low for large date range requests.
Skip if you need intraday data, since Frankfurter returns daily observations only from most providers.
The public API requires no authentication, no SDK, and no monthly registration. A plain `curl` or `fetch` call returns JSON. For teams that want zero external dependencies, the Docker image is a one-command deploy on any server.
Skip if your production environment requires a commercially backed SLA with uptime guarantees, since the public API is a community-hosted instance with no SLA.
Most applications that handle money need reliable exchange rates: invoicing in multiple currencies, displaying prices by region, calculating taxes, or reporting financials. The options have historically meant either building against a paid API subscription or scraping central bank sites that weren't designed for programmatic access.
Paid exchange rate APIs charge monthly fees even for modest call volumes, often with tiered pricing that restricts history depth, rate-of-change data, or the number of currencies available at lower price points. Developer teams with tight budgets or privacy requirements end up either over-paying for capabilities they only partially use or accepting data gaps when they hit rate limits.
Rates for 219 fiat currencies and 39 other assets, blended from 111 central banks and official providers. Each blended rate names which providers contributed, so you can filter to a specific source for compliance or audit purposes.
The default EUR-based blended feed goes back to January 1948, covering decades of currency regime changes and monetary history. Use the /v2/coverage endpoint to find the exact date range a given currency pair supports before building a query.
The public instance at api.frankfurter.dev is free for all uses including commercial. There are no monthly or daily caps; requests are rate-limited to prevent abuse but not metered. For high-volume needs, the Docker image lets you run your own instance.
Run your own instance with a single `docker run` command. Mount a volume for SQLite persistence and add optional free API keys for providers that require registration (Bank of Morocco, Federal Reserve, Bank of Thailand, and others). The deploy guide covers production configuration.
By default the API returns JSON. Append `.csv` or set the Accept header to `text/csv` for spreadsheet-friendly output. For large time series, request NDJSON (application/x-ndjson) to stream results line by line without buffering the full dataset in memory.
The project ships an MCP (Model Context Protocol) server, so AI agents can query exchange rates and time series without custom glue code. Point the agent at the project's llms.txt file for LLM-readable documentation of the API.
Open Exchange Rates is a paid JSON API covering 200+ currencies with commercial-use licensing tiers. Both provide daily reference rates and historical data via REST, so the core overlap is significant.
| Feature | Frankfurter | Open Exchange Rates |
|---|---|---|
| License | MIT | Proprietary |
| Self-hosting | Yes (Docker) | No |
| Pricing | Free | From $12/month |
| History depth | Back to 1948 | Varies by plan |
| API key required | No (public instance) | Yes |
Frankfurter is the better choice when you need no-cost access, self-hosting for data ownership, or historical rates back to the 1940s. Open Exchange Rates is worth considering when you need an SLA-backed service with premium support, guaranteed uptime, or hourly rate updates on paid plans, and your budget allows for a subscription.
Fixer covers 170 currencies with real-time, hourly, and historical data, operating as a managed service with no self-hosting path.
| Feature | Frankfurter | Fixer |
|---|---|---|
| License | MIT | Proprietary |
| Self-hosting | Yes | No |
| Pricing | Free | From $14.99/month |
| Currency count | 219 | 170 |
| API key required | No | Yes |
Frankfurter covers more currencies than Fixer (219 vs 170) and requires no signup. Fixer is worth considering for teams that need a commercially supported SLA, intraday rate updates, or integration with existing Fixer client libraries already in their stack.
CurrencyAPI covers 170+ fiat currencies, 16 cryptocurrencies, metals, and accounting averages, with enterprise customers including SAP and Heineken.
| Feature | Frankfurter | CurrencyAPI |
|---|---|---|
| License | MIT | Proprietary |
| Self-hosting | Yes | No |
| Pricing | Free | Free tier, then paid |
| Crypto coverage | Thin (mainstream only) | 16 currencies |
| OHLC data | No | Yes |
For applications that need OHLC (open/high/low/close) data or broad cryptocurrency coverage beyond the handful of mainstream coins Frankfurter provides, CurrencyAPI is the stronger choice. For standard fiat currency conversion, billing, and reporting with no budget for a data subscription, Frankfurter covers the same use cases at no cost.
Deploy the API server with Docker for self-hosted exchange rate data.
```bash
docker run -d --init -p 8080:8080 lineofflight/frankfurter
```Yes. The hosted API at api.frankfurter.dev is free for all commercial applications with no usage caps. Blended rates (the default) are Frankfurter's own calculations and carry no provider licensing restrictions. If you query a specific provider's endpoint directly, that provider's terms apply.
Yes. The Docker image at lineofflight/frankfurter runs the full API stack. A single docker run -d --init -p 8080:8080 lineofflight/frankfurter command starts an instance. For production, mount a volume to persist the SQLite database across restarts and add optional API keys for providers that require registration (FRED, Bank of Thailand, Bank of Morocco, and others).
No. Frankfurter publishes reference rates from central banks and official sources, which update once or a few times per day. The project FAQ states it is not built for live trading or exotic currencies with high intraday swings. Applications that need tick-level or minute-level rate data should use a dedicated forex data provider.
The API covers 219 fiat currencies and 39 other assets, including precious metals (gold, silver, platinum, palladium) and some mainstream cryptocurrencies (BTC, ETH, SOL, XRP, and stablecoins). The project notes that crypto coverage is thin. Use the /v2/currencies endpoint to see the full list with provider coverage details.
No. The public instance does not log IP addresses, request URLs, or personal data. The project documentation states this explicitly and notes that queries qualify as Data Not Collected under Apple and Google Play guidelines. The public instance runs behind Cloudflare, which provides only aggregate traffic statistics.
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