# MeshId

> A session-unique identifier for trackables in the environment, e.g., planes and feature points.

## Definition

* **Type:** Struct
* **Namespace:** [UnityEngine.XR](/engine/6000.7/script-reference/unityengine/xr.md)
* **Assembly:** UnityEngine.XRModule
* **Implements:** [IEquatable\<MeshId>](https://learn.microsoft.com/dotnet/api/system.iequatable-1)

```csharp
public struct MeshId : IEquatable<MeshId>
```

## Remarks

Ids are generally unique to a particular `XRSessionSubsystem`, but multiple sessions may produce identical ids for different trackables.

## Static Properties

| Property                                                                        | Description               |
| ------------------------------------------------------------------------------- | ------------------------- |
| [InvalidId](/engine/6000.7/script-reference/unityengine/xr/meshid/invalidid.md) | Represents an invalid id. |

## Methods

| Method                                                                        | Description                                     |
| ----------------------------------------------------------------------------- | ----------------------------------------------- |
| [ToString](/engine/6000.7/script-reference/unityengine/xr/meshid/tostring.md) | Generates a nicely formatted version of the id. |