# Assert Value

Documentation owner: module `pipes`; documentation version: `2026.117`.
Source: `content/modules/pipes/2026.117/valves/flow/assert-value.mdx` at commit `205d3802b68fb9e948e43600f3f9080789c5ae0d`.

## Introduction

Valve for asserting the result of an expansion expression.

Applies a regular expression on the expansion result. If value is null or expression doesn't match; Flow will fail.

Use this valve validate the input to your pipe.

## Configuration

:::note
**Valve name:** `AssertValue`
:::

### Properties

| Name | Description | Default value | Mandatory | Expanded |
| --- | --- | --- | --- | --- |
| `value` | Value to assert |  | Yes | Yes |
| `regex` | Regular expression |  | Yes | No |

### Example

```json
{
  "name": "AssertValue",
  "config": {
    "value": "${request.username}",
    "regex": "[a-z]{8,}"
  }
}
```