> 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/data-api-sdk/authentication-users-and-connection-state/user-uniqueness-reference-id.md).

# Why are multiple user\_ids created for one reference\_id?

Each Terra `user_id` represents a **single user-provider connection**, and every data request is scoped to one `user_id` (one call returns one provider's data).

`reference_id` is purely metadata to help you reconcile users on your side. It carries no dedup logic, so `reference_id` + provider does not guarantee a unique record. A previous `user_id` is only replaced (via a reauth event) when the same provider account is authenticated again under the same developer ID.

Two active connections sharing a `reference_id` and provider but with different `user_id`s usually means the user connected from two different devices or accounts.

To combine providers for one end user:

* Make separate calls per `user_id`.
* Map them via the `reference_id` supplied at [authentication](https://docs.tryterra.co/health-and-fitness-api/user-authentication).

Filtering below the data-type level must be done in your own application logic.


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.tryterra.co/faq/help-topics/data-api-sdk/authentication-users-and-connection-state/user-uniqueness-reference-id.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.