Languages and currencies
The buyer pages and the buyer's mails in the buyer's language; the price in their currency.
Everything a buyer sees and every mail a buyer gets is in their language: the tool's page, sign-in, the account with its licences, devices and seats, the page after a purchase, and the mails — the sign-in link, the licence, a resent key, a team licence. The dashboard, the docs and the API stay in English, as Stripe's do.
The languages
English, German, French, Spanish, Italian, Portuguese, Dutch and Greek. The page is in the browser's language when it is one of these, else English; a switcher in every buyer footer lets the buyer choose, and the choice is kept for a year. The <html lang> follows, so screen readers do too.
A mail is in the language of the request that caused it: the sign-in form's browser, the checkout. A licence remembers the language it was bought in, so a key the developer resends months later, or a seat given from a team licence, is still in the buyer's language.
What stays as you wrote it
Your tool's name, tagline and description are your words, in the language you wrote them; the Wall does not translate them. If you sell to one market, write them for it; the frame around them — plans, facts, buttons, notes — is translated whatever you wrote.
Stripe's own page speaks the buyer's language too: the Wall passes it along.
Prices in the buyer's currency
You set prices in your own currency, on your own Stripe account. At checkout, Stripe's Adaptive Pricing shows the amount in the buyer's local currency where it can — a buyer in the United States sees dollars for a euro price, with the rate on the page — and the buyer pays Stripe's conversion fee (2–4%, inside the shown amount); you settle in your currency as always, and a refund goes back in theirs at the same rate. Your own page still shows the price in your currency, formatted for the buyer's language, with one line saying Stripe will show it in theirs.
It applies where Stripe supports it, for prices in one of your settlement currencies; elsewhere the buyer pays in your currency, as before. Nothing to set.
Testing another language
Change the browser's language, or use the switcher. To see a checkout in another currency in test mode, pay with an address such as test+location_US@example.com: Stripe presents its page as it would to a buyer there.