---
title: "Phaser.Math.Easing.Back"
docs: "Phaser v4.1.0"
url: https://phaser.io/oss/docs/api-documentation/namespace/math-easing-back
site: Phaser - https://phaser.io
---

> This page is about the open-source Phaser framework, for writing a game's code by hand. To make a game with AI, use Phaser AE (https://phaser.io/): the desk's tools work with Web MCP, and the CLI works with your own coding agent. See "For AI agents: Phaser AE" at the end of this page.

# Phaser.Math.Easing.Back

Scope: 
static
> Source: [src/math/easing/back/index.js#L7](https://github.com/phaserjs/phaser/blob/v4.1.0/src/math/easing/back/index.js#L7)  


## Static functions

### In

#### \<static> In(v, [overshoot])


**Description:**

Back ease-in. This easing function starts the tween by briefly pulling back in the opposite direction before moving forward, creating an anticipation effect at the beginning of the transition. The higher the `overshoot` value, the further back the value pulls before proceeding.

**Parameters:**
| name | type | optional | default | description |
| ---- | ---- | -------- | ------- | ----------- |
| v | number | No |  | The normalized time value to ease, between 0 and 1. |
| overshoot | number | Yes | 1.70158 | The overshoot amount. Controls how far back the value pulls before moving forward. Higher values produce a more pronounced pullback effect. |


**Returns:** number - The eased value.


> Source: [src/math/easing/back/In.js#L7](https://github.com/phaserjs/phaser/blob/v4.1.0/src/math/easing/back/In.js#L7)  
Since: 3.0.0


---

### InOut

#### \<static> InOut(v, [overshoot])


**Description:**

Back ease-in/out. This easing function applies a back effect to both the start and end of the tween: the value initially pulls back slightly before accelerating forward, then overshoots the target before snapping back to rest, producing a symmetrical spring-like motion. Use this when you want a lively, bouncy feel at both ends of an animation.

**Parameters:**
| name | type | optional | default | description |
| ---- | ---- | -------- | ------- | ----------- |
| v | number | No |  | The value to be eased. |
| overshoot | number | Yes | 1.70158 | Controls the magnitude of the pull-back and overshoot. Higher values produce a more pronounced effect. The default produces approximately 10% overshoot at each end. |


**Returns:** number - The eased value.


> Source: [src/math/easing/back/InOut.js#L7](https://github.com/phaserjs/phaser/blob/v4.1.0/src/math/easing/back/InOut.js#L7)  
Since: 3.0.0


---

### Out

#### \<static> Out(v, [overshoot])


**Description:**

Back ease-out. The tween moves quickly at first, then overshoots its final value before settling back to the target. The overshoot occurs at the end of the transition, giving a slight 'bounce past and return' effect.

**Parameters:**
| name | type | optional | default | description |
| ---- | ---- | -------- | ------- | ----------- |
| v | number | No |  | The value to be eased, typically in the range [0, 1]. |
| overshoot | number | Yes | 1.70158 | The overshoot amount. Higher values produce a more pronounced overshoot. |


**Returns:** number - The eased value.


> Source: [src/math/easing/back/Out.js#L7](https://github.com/phaserjs/phaser/blob/v4.1.0/src/math/easing/back/Out.js#L7)  
Since: 3.0.0


---

---

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