# Validation Rules

{% hint style="info" %}
Registration Authority validation rules can only be written and assigned by Registration Authority Managers and Registrars, or Registry Administrators.

Registry-wide validation rules can only be written and assigned by Registry Administrators.
{% endhint %}

Validation Rules allow Registration Authority Managers and Registrars to set business rules for metadata within their Registration Authority, or Registry Administrators to set registry-wide rules for all content.

Validation Rules can be used to specify:

* Mandatory fields
* Uniqueness of fields
* Length of fields
* Formats of names.

### Validation Rule Functionality

Validation rules can be:

* Written (as [YAML](https://en.wikipedia.org/wiki/YAML) regular expressions)
* Assigned to either:
  * A Registration Authority
    * Whether a metadata item passes or fails a Registration Authority validation rule's checks, this will display against its [review request](/collaborating-within-the-registry/opening-a-review.md) when one is opened using that Registration Authority
    * Validation rules can only be written for Registration Authorities by Managers or Stewards of that Registration Authority, or Registry Administrators
  * The entire registry
    * When a registry-wide validation rule is written, it will apply to any and all metadata items that fit its criteria, and display its checks against those items' review requests when one is opened using any Registration Authority
    * Registry-wide validation rules can only be written by Registry Administrators.


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