Standard rules engine reference for Azure CDN

In the Standard rules engine for Azure Content Delivery Network (Azure CDN), a rule consists of one or more match conditions and an action. This article provides detailed descriptions of the match conditions and features that are available in the Standard rules engine for Azure CDN.

The rules engine is designed to be the final authority on how specific types of requests are processed by Standard Azure CDN.

Common uses for the rules:

  • Override or define a custom cache policy.
  • Redirect requests.
  • Modify HTTP request and response headers.

Terminology

To define a rule in the rules engine, set match conditions and actions:

Azure CDN rules structure

Each rule can have up to ten match conditions and five actions. Each Azure CDN endpoint can have up to 25 rules.

Included in this limit is a default global rule. The global rule doesn't have match conditions; actions that are defined in a global rule always triggered.

Important

The order in which multiple rules are listed affects how rules are handled. The actions that are specified in a rule might be overwritten by a subsequent rule.

Limits and pricing

Each Azure CDN endpoint can have up to 25 rules. Each rule can have up to ten match conditions and five actions. Pricing for Rules Engine follows the below dimensions:

  • Rules: $1 per rule per month
  • Requests Processed: $0.60 per million requests
  • The first 5 rules will remain free

Syntax

How special characters are treated in a rule varies based on how different match conditions and actions handle text values. A match condition or action can interpret text in one of the following ways:

Literal values

Text that's interpreted as a literal value treats all special characters except the % symbol as part of the value that must be matched in a rule. For example, a literal match condition set to '*' is satisfied only when the exact value '*' is found.

A percent sign is used to indicate URL encoding (for example, %20).

Wildcard values

Currently we support the wildcard character in the UrlPath Match Condition in Standard Rules Engine. The * character is a wildcard that represents one or more characters.

Next steps