Where the exchange rates come from

The source

Rates come from a public exchange-rate feed at open.er-api.com, requested directly by the app and by this website. There is no server of ours in between, no key and no account, and the request carries nothing about you. Every figure is quoted against the US dollar and cross rates are one division and one multiplication — no second request, no drift.

How often they update

The feed publishes about once a day. The app fetches when it opens and when its copy is more than three hours old, and you can pull down on the board to ask again. The website shows the rate as of the time the page was built and, when your browser is online, loads the current figure on top.

What “mid-market” means

The mid-market rate is the midpoint between the price at which the currency is bought and the price at which it is sold on the open market. It is the rate you see quoted in the news, and it is the rate no consumer actually gets: a card adds a margin, a bureau adds a larger one, and a shop offering to charge you in your own currency adds the largest of all.

Currencies with no rate

A currency the feed does not carry is shown with no rate rather than an invented one. In the app you can type in a rate yourself, and it outranks every other source for that currency until you clear it.

Provenance on every figure

The app never shows a converted number without saying which of four sources it came from — live, cached, built in, or set by you — and how old it is. A number with no provenance is a rumour.

Not financial advice

Rates are indicative. Do not use them as the basis of a financial, commercial or legal decision.