Custom rules allow you to control incoming traffic by filtering requests to a zone. You can perform actions like *Block* or *Managed Challenge* on incoming requests according to rules you define.

Like other rules evaluated by Cloudflare's [Ruleset Engine](https://developers.cloudflare.com/ruleset-engine/), custom rules have the following basic parameters:

* An [expression](https://developers.cloudflare.com/ruleset-engine/rules-language/expressions/) that specifies the criteria you are matching traffic on using the [Rules language](https://developers.cloudflare.com/ruleset-engine/rules-language/).
* An [action](https://developers.cloudflare.com/ruleset-engine/rules-language/actions/) that specifies what to perform when there is a match for the rule.

The [custom rules documentation](https://developers.cloudflare.com/waf/custom-rules/) includes examples for common use cases.

## Skip rules

You can skip one or more Cloudflare security features using a custom rule [configured with the *Skip* action](https://developers.cloudflare.com/waf/custom-rules/skip/). These rules are also known as skip rules. Refer to [Skip options](https://developers.cloudflare.com/waf/custom-rules/skip/options/) for more information on the features you can skip.
