---
title: FixedUpdate.PhysicsCore2DFixedUpdate
product: Unity Editor
version: '7000.0'
latest_version: '7000.0'
status: This page documents version 7000.0. The latest version is 7000.0.
canonical: https://docs.unity.com/en-us/engine/7000.0/script-reference/unityengine/playerloop/fixedupdate/physicscore2dfixedupdate
latest_url: https://docs.unity.com/en-us/engine/7000.0/script-reference/unityengine/playerloop/fixedupdate/physicscore2dfixedupdate.md
last_updated: 2026-10-29
generated_at: 2026-11-04T05:56:54.685Z
locale: en-us
---

# FixedUpdate.PhysicsCore2DFixedUpdate

> Native Player loop system that simulates the low-level 2D physics worlds in the Unity.U2D.Physics namespace that are set to simulate in the fixed update.

## Definition

* **Type:** Struct
* **Namespace:** [UnityEngine.PlayerLoop](/engine/7000.0/script-reference/unityengine/playerloop.md)
* **Assembly:** UnityEngine.CoreModule

```csharp
public struct FixedUpdate.PhysicsCore2DFixedUpdate
```

## Remarks

This system simulates only physics worlds whose simulation type is set to `FixedUpdate`, which is the default, using [Time.fixedDeltaTime](/engine/7000.0/script-reference/unityengine/time/fixeddeltatime.md). Worlds set to simulate in the Update loop are simulated in `PreLateUpdate.PhysicsCore2DLateUpdate`. This system also sends Transform change callbacks when the transform change mode is set to `FixedUpdate`. This system is active only in Play mode.

This struct identifies a native system in the Player loop. It has no members, and the system's update logic runs in native engine code. Use this type with [PlayerLoopSystem.type](/engine/7000.0/script-reference/unityengine/lowlevel/playerloopsystem/type.md) to find the system when you reorder, replace, or remove it in a custom Player loop. For more information, refer to [Customizing the Player loop](/engine/7000.0/manual/scripting/managing-update-order/player-loop-customizing.md).