Learn

Guides, tutorials, and references

How to read exchange rates, build a time series, tell live spot from a reference fix, and wire the API into Python, JavaScript, or an LLM agent.

TutorialHow to get exchange rates in PythonRead live and historical FX rates in Python with a few lines of code. No key to start, 50,000 calls a month once you sign up, and every response tells you how fresh the rate is.5 min read TutorialCurrency conversion in JavaScript and Node.jsFetch live exchange rates and convert amounts in JavaScript using the global fetch API. Works in Node 18+, Deno, Bun, and modern browsers. No key to start, 50,000 calls a month on the free tier.5 min read GuideHistorical FX rates and time series in one callPull a multi-currency FX series across a date range with a single request to /v1/range. Daily history back to 1999, returned as a data array of daily rows ready to load into pandas.6 min read GuideHow to backfill FX rates without look-ahead biasWhen you reconstruct a historical EUR/USD series for analytics or backtesting, the rate you query must be the one that was knowable on each simulated date, not a value published later. Here is the pattern.6 min read ReferenceReading source and market_session in your pipelineEvery exchangerate.dev response carries two freshness fields: source and market_session. Together they tell you exactly what you are looking at, and whether to accept that rate or wait for a fresher one.5 min read GuideIndicative vs executable FX rates: what a rates API actually gives youEvery FX rate you read from an API is one of two things: a reference price for analysis and display, or a dealer quote you can trade on. These are not interchangeable. Knowing the difference determines whether you are building the right thing.6 min read GuideECB reference rates, explainedThe European Central Bank publishes one official FX reference rate per business day. Here is what that means, how it differs from live spot data, and how to read it from the API.6 min read BlogWhat ECB-based FX APIs miss on weekendsThe ECB publishes its reference fix once per business day. On Saturday and Sunday it publishes nothing, so any API sourced only from that fix freezes at Friday's value until Monday. Here's what that means for a "latest" endpoint, and how live-sourced data differs.5 min read GuideComing from Frankfurter? Here is the mapping.Frankfurter is a solid open-source project backed by ECB data. If you want an API key, weekend coverage, and freshness metadata, this guide shows exactly what changes.6 min read ComparisonHow to compare free exchange-rate APIs in 2026Picking a free FX data source is not just about the price. Six dimensions matter: quota, weekend freshness, freshness metadata, history depth, a conversion endpoint, and agent support. Here is how to think through each one.6 min read GuideGive your LLM agent live FX rates over MCPexchangerate.dev runs a Model Context Protocol server so an LLM agent can request currency rates as structured tool calls, without writing a line of REST client code.6 min read