Mid-market rate with a sanity-check spread, for quotes and invoices.
The everyday operating tools of a one-to-five-person business: shrink a product photo for the marketplace, generate a QR code for the storefront, check the exchange rate before quoting a customer, generate UUIDs for an import, summarize a competitor blog post, count the words on a product description. Cheap, fast, and your inventory photos never leave your device.
The rate you and the customer agree on. The published rate is a reference, and your bank will hand you a worse one - so if you quote at the reference rate, add a small buffer or state the rate and date on the document.
It is fetched live from a public rate source each time you convert, so it reflects the latest published reference rate rather than a snapshot from months ago. For a contract, note the timestamp you used.
Banks and payment providers earn a margin on the spread, so the rate you actually receive is worse than the published reference. Compare the all-in amount you get, not the headline rate.