1. 01Choose the source and target currencies, or use the swap button to switch them.
2. 02Type an amount on either side and the other side converts instantly at the currently cached rate.
3. 03Read the data date, data source and current exchange rate shown on the page.
4. 04Click refresh to update; when a cache from within the last 12 hours exists, simply opening the page uses it first.

Main data source

— the latest USD rates from Frankfurter; the implementation also requests USD rates from open.er-api.com as a supplement/fallback so that more currencies are covered.

Cache

— rates are cached in the browser's localStorage with a 12-hour TTL; a manual refresh skips a fresh cache and requests new data.

Failures

— if both online sources fail, an older cache is still shown with a warning; with no cache at all, conversion cannot be completed.

Reference data

— the page shows reference mid-market rates and does not include bank spreads, fees, card settlement prices or live trading quotes.

What it does not do

— it does not predict rates, execute exchanges or keep transaction records.

Amounts are used only for calculation in your browser; the network request only fetches public USD rate data and never sends the amount you typed to a rate service, and the selected currency pair is stored in your browser.