> For the complete documentation index, see [llms.txt](https://gebra-it.gitbook.io/wiki/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://gebra-it.gitbook.io/wiki/configuration/app-editor/app-editor-properties/inputmaskregex.md).

# InputMaskRegEx

1. Input Mask Regex

You can mask the uinput of a textbox by using a regular expression.

You can find further information for for the Input Mask itself \[here]\(<https://github.com/RobinHerbots/Inputmask>)

If you want to lear more about regex, take a look \[here ]\(<https://regex101.com/>)

Examples:

This allows only non-capital and capital letters (azA-Z) numbers (0-9) and the underscore (\_). But no special characters (like ö, &, %, @,...).

```
^[_0-9a-zA-Z]*$
```

Example 2. This forces the input to begin with abc, followed by any a-Z0-9

```
^abc[_0-9a-zA-Z]*$
```