# External profile data

Your system may associate an Umbraco Engage visitor with other data coming from an external system such as a Customer Relation Management (CRM) system.

If you want to use external data in a custom segment you have to write the data access yourself in the custom segment code. Learn more about this in the [Profiling section for Developers](/umbraco-engage/developers/profiling/external-profile-data.md).

![External profile data tab](/files/aN1PtXzq0bgdhexIA4o1)


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# Agent Instructions: 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.umbraco.com/umbraco-engage/marketers-and-editors/profiling/external-profile-data.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.