> For the complete documentation index, see [llms.txt](https://docs.tryterra.co/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.tryterra.co/faq/help-topics/connecting/end-user-authentication-and-sso/provider-page-language-not-controllable.md).

# Why do provider OAuth pages always show in English?

The `language` parameter on session / auth-URL generation only controls the **Terra widget interface**, not the provider's own login page.

Each provider controls its auth-page language itself, typically via browser `Accept-Language` headers or its own locale routing. Some, like Fitbit, only offer English.

Passing a provider-page locale through Terra's generated auth link is **not currently supported** for most providers.