> For the complete documentation index, see [llms.txt](https://redd.gitbook.io/react-advanced-form/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://redd.gitbook.io/react-advanced-form/getting-started/validation-rules.md).

# Validation rules

The purpose of a form is to validate the entered data. Unlike other solutions, where a developer is given a single `validate` function, React Advanced Form uses smart built-in validation algorithm based on the [Validation schema](/react-advanced-form/validation/schema.md). It is a convenient functional way of declaring validation rules, from simple to complex. 

This part is going to focus on how to declare a validation schema and write the rules. We are going apply the validation rules and messages to the forms in the next part.

{% content-ref url="/pages/-LDfz\_oSEEoL-XYGJM2g" %}
[Getting started](/react-advanced-form/validation/getting-started.md)
{% endcontent-ref %}