Frankfurter (open source, ECB data)

Frankfurter — ECB reference rates as a clean JSON API — thirty currencies, history to 1999, no key

When you need reference exchange rates — one fix per day, any base, any of thirty currencies, back to 1999 — with the simplest API on this list, for charts, conversions and notebooks.

fxglobaleuro area

Asset classesfx

Frequencydaily

History1999 → today

Limit · costNo key · no published limit; self-hostable

KeyNo key

Formats · pull withjson — python, excel, sheets

LicenceMIT-licensed software serving ECB reference rates; the ECB permits free use with attribution.

RedistributeWith attribution; check series notes

Best for“A daily FX series for any major pair with one URL” · “Converting a series into another currency”

When to use it

Reach for it when…

When you need reference exchange rates — one fix per day, any base, any of thirty currencies, back to 1999 — with the simplest API on this list, for charts, conversions and notebooks.

Not for: Intraday rates or Asian-morning freshness (the ECB fixes at about 16:00 CET), currencies outside the ECB's list, anything requiring a trading price.

How to read it

Units, revisions, traps

Units. Units of the quote currency per one unit of the base; the ECB's own base is the euro and other bases are cross-computed.

Revisions. Not revised.

One fix per business day; weekends and ECB holidays return the previous fix.
Cross rates via the euro can differ slightly from a direct market quote.
The date range endpoint returns a dict keyed by date; pandas needs a transpose.

Classic mistake: Using the 16:00 CET fix as 'today's rate' in an Asian morning newsletter.

How to use it in your own work

Three recipes

Recipe 1 · A pair's daily history
Recipe 2 · Latest rates for one base
Recipe 3 · Convert a series into another currency

Each recipe: Python · Excel · Sheets, with how to read the result. Python recipes run under pandas; recipe 1 is re-run by the weekly check where the source allows it.

How to use it in your own work

Copy the snippet, change the series id, read the result the way the footer says. Replace YOUR_…_KEY with your own key where one is needed.

Recipe 1A pair's daily history

import requests, pandas as pd
u = "https://api.frankfurter.dev/v1/2024-01-01..?base=USD&symbols=KRW,JPY"
j = requests.get(u, timeout=30).json()
df = pd.DataFrame(j["rates"]).T
df.index = pd.to_datetime(df.index)
print(df.sort_index().tail())

How to read the resultWon and yen per dollar; both rising is a dollar move, one rising is a local one.

Recipe 2Latest rates for one base

import requests, pandas as pd
j = requests.get("https://api.frankfurter.dev/v1/latest?base=SGD", timeout=30).json()
print(j["date"]); print(pd.Series(j["rates"]).sort_values().head())

How to read the resultCross rates computed through the euro from the same fix.

Recipe 3Convert a series into another currency

# a monthly series in USD (say, an index) into EUR at month-end fixes
import requests, pandas as pd
fx = pd.DataFrame(requests.get("https://api.frankfurter.dev/v1/2023-01-01..?base=USD&symbols=EUR", timeout=30).json()["rates"]).T
fx.index = pd.to_datetime(fx.index)
monthly = fx["EUR"].resample("ME").last()
print(monthly.tail())

How to read the resultResample to the same frequency as the series you are converting before multiplying.

Series → question map

The ids we use from Frankfurter, each with the question it answers. The catalog's compare view reads the concept tags behind these rows.

Series	Answers	Region	Concept
latest?base=USD	Today's reference rates against the dollar	global	fx_cross
..?base=USD&symbols=KRW	Won per dollar, daily reference	Korea	fx_usd
..?base=USD&symbols=JPY	Yen per dollar, daily reference	Japan	fx_usd
..?base=EUR&symbols=USD	Dollars per euro, daily reference	euro area	fx_usd

Compare with

Same question, different source: ECB Data Portal, FRED, BOK ECOS. The compare view lines up coverage, frequency, history and access side by side and lists what the combination makes possible.

Open compare: Frankfurter · ECB Data Portal · FRED →

Curated: Is the won weak or the dollar strong?.

Questions readers ask

Is Frankfurter free?

Yes, no key; the software is open source and can be self-hosted.

Which currencies?

The ECB's reference list — about thirty, including USD, JPY, KRW, CNY, SGD, GBP, AUD, INR, MYR, THB, IDR, PHP.

When does it update?

Once a day, shortly after the ECB's 16:00 CET fix.

From the paper

Is the won weak, or is the dollar strong?Financial Literature Asia · 8 Sept 2026
🌍 5.28% — Britain's ten-year borrowing cost, the highest since 2008Financial Literature Europe · 2 Sept 2026
🌍 3.3% — energy pushed euro-area inflation up; core slipped to 2.4%Financial Literature Europe · 1 Sept 2026

Educational only — we explain, we never advise · snippet licence: public domain · corrections to [email protected], fixed within a day and logged in the changelog.