ExchangeRate-API's open endpoint at https://open.er-api.com/v6 returns daily rates for one base currency, updated once a day.
None for the open endpoint. Its terms ask for an attribution link to exchangerate-api.com where the rates are shown.
Full reference: https://www.exchangerate-api.com/docs/free
curl https://open.er-api.com/v6/latest/USD{
"result": "success",
"provider": "https://www.exchangerate-api.com",
"documentation": "https://www.exchangerate-api.com/docs/free",
"terms_of_use": "https://www.exchangerate-api.com/terms",
"time_last_update_unix": 1790121751,
"time_last_update_utc": "Wed, 23 Sep 2026 00:02:31 +0000",
"time_next_update_unix": 1790209981,
"time_next_update_utc": "Thu, 24 Sep 2026 00:33:01 +0000",
"time_eol_unix": 0,
"base_code": "USD",
"rates": {
"USD": 1,
"AED": 3.6725,
"AFN": 64.786648,
"ALL": 79.800421,
"AMD": 363.633322,
"ANG": 1.79,
"AOA": 929.074139,
"ARS": 1513.6838,
"AUD": 1.406391,
"AWG": 1.79,
"AZN": 1.700833,
"BAM": 1.707894,
"BBD": 2,
"BDT": 122.85949,
"BGN": 1.707894
}
}