# Masks

The MaskedTextBox supports a set of built-in masks and also enables you to set your own custom mask rules and implement static symbols (literals) in the mask pattern.

## Mask Rules

The MaskedTextBox supports the following built-in mask rules:

* `0`—Requires a digit (0-9).
* `9`—Requires a digit (0-9) or a space.
* `#`—Requires a digit (0-9), space, plus (+), or minus (-) sign.
* `L`—Requires a letter (a-Z).
* `?`—Requires a letter (a-Z) or a space.
* `A`—Requires an alphanumeric (0-9, a-Z).
* `a`—Requires an alphanumeric (0-9, a-Z) or a space.
* `&`—Requires a character (excluding space).
* `C`—Requires a character or a space.

> - If any of the built-in masks accepts spaces, set the [`promptPlaceholder`](https://www.telerik.com/kendo-angular-ui-develop/components/inputs/api/maskedtextboxcomponent#promptplaceholder) to a character that is not allowed by the mask.
> - To escape a mask rule, use the slash (`\`) character. An escaped rule turns into a literal.

The MaskedTextBox also allows you to define custom mask rules by setting the [`rules`](https://www.telerik.com/kendo-angular-ui-develop/components/inputs/api/maskedtextboxcomponent#rules) property.

Apart from the built-in and custom rules, you can also use static symbols in the mask pattern that are also known as literals. In the masked value, a literal is always rendered on the same position as the position where it is defined in the `mask` property.

The following example demonstrates how to use the digit-requiring mask (`0`) and the literal (`-`) of the MaskedTextBox.

[Demo Source](https://demos.telerik.com/kendo-angular-ui/demos/inputs/maskedtextbox/masks1/source.txt)

The following example demonstrates how to extend the available mask rules.

[Demo Source](https://demos.telerik.com/kendo-angular-ui/demos/inputs/maskedtextbox/masks2/source.txt)

## Masks on Input Values or Focus

By default, the MaskedTextBox always renders a mask. To display the mask only when the input contains a value or is focused, use the [`maskOnFocus`](https://www.telerik.com/kendo-angular-ui-develop/components/inputs/api/maskedtextboxcomponent#maskonfocus) option. `maskOnFocus` is particularly useful in combination with [floating labels](https://www.telerik.com/kendo-angular-ui-develop/components/labels/api/floatinglabelcomponent).

[Demo Source](https://demos.telerik.com/kendo-angular-ui/demos/inputs/maskedtextbox/masks3/source.txt)

## Suggested Links

* [API Reference of the MaskedTextBox](https://www.telerik.com/kendo-angular-ui-develop/components/inputs/api/maskedtextboxcomponent)