Guides
Integrations that hold up past the demo.
Each guide is written against the endpoint contract on this site, so the code runs as printed. They cover the parts that usually break later: where the key lives, what to retry, how long to cache, and how to keep a displayed figure honest about its age.
Start here
Guide
Free currency API with no API key: rates in five lines
The fastest possible start: one fetch, no credential, no signup.
Beginner · 4 min
Guide
Fetch exchange rates in JavaScript (fetch API, retries, caching)
From a bare fetch to something you would actually ship.
Intermediate · 9 min
Guide
Exchange rates in Python with requests (and converting a price list)
A small, typed Python module that turns one reading into a converted price list.
Beginner · 8 min
Guide
Build a React currency converter with live rates
One hook, one component, real formatting, no key in the browser.
Intermediate · 10 min
Guide
Historical exchange rates by date: ranges, snapshots and series
Date ranges, the snapshots parameter, and turning readings into a chart.
Intermediate · 8 min
Guide
Fetch exchange rates in PHP (cURL, Laravel and money that never loses a cent)
Plain cURL, a shared cache entry, and bcmath where a float would round badly.
Intermediate · 8 min
Guide
Exchange rates in Go: a typed client, one cached reading, correct rounding
net/http, typed structs, a mutex-guarded cache and rounding you can defend.
Intermediate · 9 min
Guide
Exchange rates in .NET: HttpClient, System.Text.Json and IMemoryCache
A typed HttpClient, records, per-base caching and decimal instead of double.
Intermediate · 9 min
Prefer the contract to a tutorial?
The API reference states every parameter, field, header and error code in one place — the guides only show them in use.