---
title: regex
description: Creates a regex validation action.
source: /actions/regex/regex.ts
contributors:
  - fabian-hiller
  - CanRau
---

import { ApiList, Property } from '~/components';
import { properties } from './properties';

# regex

Creates a [regex](https://en.wikipedia.org/wiki/Regular_expression) validation action.

```ts
const Action = v.regex<TInput, TMessage>(requirement, message);
```

## Generics

- `TInput` <Property {...properties.TInput} />
- `TMessage` <Property {...properties.TMessage} />

## Parameters

- `requirement` <Property {...properties.requirement} />
- `message` <Property {...properties.message} />

### Explanation

With `regex` you can validate the formatting of a string. If the input does not match the `requirement`, you can use `message` to customize the error message.

> Hint: Be careful with the global flag `g` in your regex pattern, as it can lead to unexpected results. See [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/test#using_test_on_a_regex_with_the_global_flag) for more information.

## Returns

- `Action` <Property {...properties.Action} />

## Examples

The following examples show how `regex` can be used.

### Pixel string schema

Schema to validate a pixel string.

```ts
const PixelStringSchema = v.pipe(
  v.string(),
  v.regex(/^\d+px$/, 'The pixel string is badly formatted.')
);
```

## Related

The following APIs can be combined with `regex`.

### Schemas

<ApiList items={['any', 'custom', 'string']} />

### Methods

<ApiList items={['pipe']} />

### Utils

<ApiList items={['isOfKind', 'isOfType']} />
