For Square-hosted checkout pages (Payment Links / Checkout API), the language is determined by the seller’s location-level language_code setting, not by the buyer. There is no per-link or per-customer locale parameter in the CreatePaymentLink API.
The below is a location-wide change and it affects all hosted checkout pages for that location.
To change the language from Japanese to English, update the location’s language_code via the Locations API:
http
PUT /v2/locations/{LOCATION_ID}
{
"location": {
"language_code": "en"
}
}
Or change it in the Square Dashboard under location settings.
If you need per-customer language control you can build your own checkout page with the Web Payments SDK instead, which supports payments.setLocale('en-US') (or zh for Chinese) to dynamically set the language on your own checkout page.
