#historical-fx

The official US government foreign-exchange rates, served live from the US Treasury's FiscalData API — no key, nothing cached. These are the rates the federal government uses to convert foreign-currency balances into US dollars for reporting, and US companies use them for tax and compliance; they are published every quarter for around 168 currencies and go back two decades. The rates endpoint returns the whole quarterly set — every country and currency with its rate to one US dollar (the euro near 0.87, the yen near 159) — and accepts a date to pull any past quarter. The currency endpoint returns one currency's official rate with its history quarter by quarter, looked up by ISO code, country or currency name. The convert endpoint turns an amount from any currency into any other, crossed through the US dollar at the official Treasury rate. Everything is the Treasury's own published data, live, nothing stored; rates are quarterly and authoritative for accounting, not a live market quote. This is the official FX layer for any accounting, tax-compliance, treasury, government-contracting or historical-FX app. Distinct from central-bank and market FX APIs — this is the US Treasury's quarterly reporting rates of exchange. 4 endpoints, no key on our side.

api.oanor.com/treasuryfx-api

Live official Czech foreign-exchange fixing, served straight from the Czech National Bank's open API — no key, nothing cached. The CNB declares one official rate per currency every working day. The rates endpoint returns the whole daily fixing — around 30 world currencies against the koruna (CZK), each with the country, the unit amount it is quoted per and the rate — and accepts a date so you can pull the official fixing for any past working day. The currency endpoint returns one currency's rate, normalised to the koruna value of a single unit, for the latest day or a chosen date — the US dollar fixed around 21 koruna in mid-2026. The convert endpoint turns an amount from any currency into any other, crossed through the koruna at the official fixing, on the latest day or a historical date. The history endpoint returns a currency's official rate over the last several working days. Everything is the central bank's own published fixing, live, nothing stored. This is the Czech koruna FX layer for any forex, payments, e-commerce, accounting or treasury app operating in Czechia and Central Europe — and a clean source of historical FX by date. Distinct from the ECB, Fed, Bank of Canada, Norges Bank, Bank of England, Brazil and Poland central-bank APIs — this is the koruna and the CNB daily fixing, queryable by date. 5 endpoints, no key on our side.

api.oanor.com/cnb-api