# UDI Identifiers

Umbraco uses Unique Document Identifiers (UDIs) to reference most object types, such as content, media, and members. A UDI contains all the metadata needed to retrieve an Umbraco object and is readable within text.

Example:

```
umb://document/4fed18d8c5e34d5e88cfff3a5b457bf2. 
```

UDIs are commonly used in Umbraco’s querying and management APIs.

## Format

A UDI consists of three parts:

1. Scheme: `umb://` – Identifies as an Umbraco UDI.
2. Type: `document`– Specifies the object type (for example, media, member, Data Type, and so on).
3. GUID Identifier: `4fed18d8c5e34d5e88cfff3a5b457bf2` – A unique identifier for the object (a GUID without dashes).

## Usage

UDIs are useful for retrieving content, media, or other Umbraco objects through the API. Below are examples of how to use a UDI in C# to get content or media.

### Retrieving Content by UDI

You can retrieve a content item using `IContentService`:

```cs
using Umbraco.Cms.Core.Services;
using Umbraco.Cms.Core.Models

@inject IContentService contentService

@{
   // Define the UDI string here
    var udiString = "umb://document/334cadfa62dd49049aad86b6e4c02aac"; // Example UDI string

   if (udiString.StartsWith("umb://document/"))
    {
        // Extract the GUID from the UDI string
        var guidString = udiString.Replace("umb://document/", "");
        if (Guid.TryParse(guidString, out var guid))
        {
            // Retrieve the content by GUID
            var content = contentService.GetById(guid);
            if (content != null)
            {
                // Access the body text field
                var bodyText = content.GetValue<string>("bodyText"); // Replace 'bodyText' with the alias of your body text field
                <p>@bodyText</p>  // Output the body text
            }
        else
            {
                <p>Content not found.</p>
            }
        }
        else
        {
            <p>Invalid GUID in the UDI string.</p>
        }
    }
}
```

## UDI Types

There are two types of UDIs in Umbraco:

### GUID UDI

Used for objects that have a GUID identifier, such as content and media.

* [API Reference: GuidUdi](https://apidocs.umbraco.com/v17/csharp/api/Umbraco.Cms.Core.GuidUdi.html)

### String UDI

Used for objects that are not GUID-based, such as dictionary items.

* [API Reference: StringUdi](https://apidocs.umbraco.com/v17/csharp/api/Umbraco.Cms.Core.StringUdi.html)


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

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

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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.