> For the complete documentation index, see [llms.txt](https://docs.umbraco.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.umbraco.com/umbraco-cms/13.latest/reference/querying/udi-identifiers.md).

# UDI Identifiers

## Introduction

Umbraco stores identifiers in UDI format for most Umbraco object types. This identifier stores all of the metadata required to retrieve an Umbraco object and is parse-able within text. Example: `umb://document/4fed18d8c5e34d5e88cfff3a5b457bf2`. UDI's can be used in many of the querying APIs.

{% hint style="info" %}
UDI is currently not an acronym for something. There is no official definition of what it's short for. Therefore it's called *UDI*
{% endhint %}

## Format

An Umbraco UDI consists of three parts: the scheme, the type and a GUID Identifier. For example: `umb://document/4fed18d8c5e34d5e88cfff3a5b457bf2`.

Breaking it down:

1. The scheme is `umb://` - this is always the same and makes it identifiable as an Umbraco UDI
2. The type is `document` - so in this is an Umbraco node, but it could also be `media`, `member`, etc.
3. The GUID Id is `4fed18d8c5e34d5e88cfff3a5b457bf2` - this is a GUID (dashes removed) which is randomly generated when the item is being created

## Usage

You can use UDIs in some of the Querying and Management/Service APIs.

There are 2 types of UDIs:

## GUID UDI

* [API Reference for Umbraco 13](https://apidocs.umbraco.com/v13/csharp/api/Umbraco.Cms.Core.GuidUdi.html)

## String UDI

* [API Reference for Umbraco 13](https://apidocs.umbraco.com/v13/csharp/api/Umbraco.Cms.Core.StringUdi.html)


---

# 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 by asking a question.

Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:

```
GET https://docs.umbraco.com/umbraco-cms/13.latest/reference/querying/udi-identifiers.md?ask=<question>&goal=<user_goal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.

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.