Currencylayer

What it covers

Currencylayer provides live quotes, historical rates, conversions, time-frame queries, and currency-change calculations. Plan entitlements determine request volume, refresh frequency, commercial use, and access to advanced operations.

Request shape

curl "https://api.currencylayer.com/live?access_key=YOUR_ACCESS_KEY&currencies=KRW,EUR"

Call the service from a backend so the access key is not exposed to visitors. Cache responses in line with the plan’s update frequency instead of spending quota on identical requests.

Key endpoints

Endpoint	Description
GET /live	Real-time exchange rates (USD base)
GET /historical	Historical rates for a date
GET /convert	Convert between currencies
GET /list	Supported currencies
GET /timeframe	Rates over a date range
GET /change	Currency change parameters

Decision notes

Currencylayer is simple to integrate, but the free plan’s non-commercial restriction is decisive for a product. Compare paid plans on quota, update frequency, source-currency switching, and overage policy.

Python example: live exchange rates (API key)

import httpx
from decimal import Decimal

API_KEY = "your_currencylayer_key"
BASE = "https://api.currencylayer.com"

def live(currencies: list[str] | None = None, source: str = "USD") -> dict[str, Decimal]:
    """Get live rates. Free plan is USD-source only and hourly."""
    params = {"access_key": API_KEY, "source": source, "format": 1}
    if currencies:
        params["currencies"] = ",".join(currencies)
    resp = httpx.get(f"{BASE}/live", params=params, timeout=30)
    resp.raise_for_status()
    data = resp.json()
    if not data.get("success"):
        raise RuntimeError(f"CurrencyLayer error: {data.get('error', {}).get('info')}")
    return {k: Decimal(str(v)) for k, v in data["quotes"].items()}

def convert(amount: Decimal, from_: str, to: str) -> Decimal:
    """Convert via USD pivot (free-plan compatible)."""
    if from_ == "USD":
        return amount * live([to])[f"USD{to}"]
    if to == "USD":
        return amount / live([from_])[f"USD{from_}"]
    usd_amount = amount / live([from_])[f"USD{from_}"]
    return usd_amount * live([to])[f"USD{to}"]

print(live(["KRW", "EUR", "JPY"]))
print("100 USD in KRW:", convert(Decimal("100"), "USD", "KRW"))

Notes:

• Key goes in access_key query param; check success field — HTTP 200 can still be an error
• Free plan: USD source only, hourly updates, 1000 calls/month — cache hard
• Quotes are keyed like USDKRW; convert non-USD pairs via the USD pivot
• For KRW-specific needs, BOK ECOS (also in this Atlas) is the authoritative free source