Bank of Korea Exchange Rate API: Official KRW Rates as JSON

Bank of Korea publishes the won's official daily exchange rates — the basic exchange rate (매매기준율, the market average rate set each business morning at 08:10 KST) for around 40 currencies — and these are the published official rates used for tax filings, audits, and compliant invoicing in South Korea, not moving market prices. This guide shows how to pull them as JSON: via a REST endpoint or the zero-dependency bok-exchange-rate npm package, with history back to 1964.

What the Bank of Korea publishes

• ~40 active currencies against the won — USD, EUR, JPY, CNY, GBP, and the full Asian and Gulf set.
• History back to 1964 — one of the deepest official series anywhere, queryable by exact date or as a time series.
• The bank's own publication date on every response, so a rate is always citable.
• No gaps to trip over — requests for weekends and Korean holidays resolve to the most recent published rates and are flagged explicitly.

The USD/KRW basic rate is the anchor of the table: it is the market average rate (MAR) computed from interbank trading and announced through Seoul Money Brokerage — the number Korean law and accounting practice reference for won conversion.

Why official rates, not market rates

A live mid-market feed answers "what is USD/KRW trading at right now?" — the right tool for checkouts and dashboards. But accountants, auditors, and tax authorities ask a different question: "which rate were you required to use for this date?" That answer comes from the central bank's published rates, and it never changes after publication.

Getting at Korea's official rates programmatically has an extra wrinkle: the Bank of Korea's registered Open API requires Korean-phone PASS identity verification to sign up, which locks out most developers outside Korea. AllRatesToday carries the same published table with no Korean registration needed.

Get the latest rates (REST)

curl "https://allratestoday.com/api/v1/central-bank/bok/latest" \
  -H "Authorization: Bearer YOUR_API_KEY"

The response is the bank's most recent published data — every rate and the publication date. The latest rates are available on every plan, including the free tier (300 requests/month, no credit card).

The npm SDK

npm install bok-exchange-rate

import { getRate, getLatestRates } from 'bok-exchange-rate';

// One pair at the official Bank of Korea rate
const pair = await getRate('USD', 'KRW', { apiKey: 'art_live_...' });
console.log(pair.rate, pair.rate_date);

// The bank's full published table
const table = await getLatestRates({ apiKey: 'art_live_...' });
console.log(table.rate_date, table.rates.length);

Zero dependencies, TypeScript types included, and it runs anywhere fetch exists — Node 18+, Bun, Deno, and edge runtimes.

Historical rates for an invoice date

import { getRatesForDate, getHistory } from 'bok-exchange-rate';

// The official rates for an invoice date — non-publication days return
// the most recent published date, flagged via published_on_requested_date.
const day = await getRatesForDate('2026-06-30', { apiKey: 'art_live_...' });

// Time series for one pair
const series = await getHistory(
  { source: 'USD', target: 'KRW', from: '2026-01-01' },
  { apiKey: 'art_live_...' }
);

Historical dates and time series need a paid plan; the latest rates stay free.

Published vs derived pairs

If the Bank of Korea does not print a pair directly, the API resolves it from the bank's published rates — an inverse, or a cross rate via KRW — and flags it derived: true with the method used. Official and computed values are never silently mixed, which is exactly the distinction an auditor will ask about.

Sixty years of won history

The series starts on 4 May 1964 — the day South Korea devalued the won to 255.77 per dollar and moved toward a unified exchange rate. From there the data traces every regime: the managed float of the 1980s, the 1997 Asian financial crisis (the won passing 1,600 per dollar), the 2008 global financial crisis, and the COVID shock of 2020. For long-run research, backtesting, or historical audit work, it is one of the deepest official exchange rate records available anywhere.

FAQ

Does Bank of Korea have an official exchange rate API?

The Bank of Korea publishes official daily rates through its ECOS statistics system, but the registered Open API requires Korean-phone identity verification, which locks out most foreign developers. AllRatesToday serves the bank's published rates as clean JSON — around 40 currencies against the won, with history back to 1964 — via REST or the bok-exchange-rate npm package. The latest table is free.

How often do Bank of Korea rates update?

Once per business day. The basic exchange rate (매매기준율, the market average rate) is set each business morning at 08:10 Korea time. These are published reference rates, not moving market prices — every API response carries the bank's own publication date so you can cite it.

Can I get the Bank of Korea rate for a past date, like an invoice date?

Yes. The /central-bank/bok/rates-for-date endpoint returns the official rates for any date back to 1964. Non-publication days resolve to the most recent published date and are flagged, so your audit trail stays honest. Historical dates require a paid plan; latest rates are free.