# How Lambda@Edge works with requests and responses
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When you associate a CloudFront distribution with a Lambda@Edge function, CloudFront intercepts requests and responses at CloudFront edge locations. You can execute Lambda functions when the following CloudFront events occur:
+ When CloudFront receives a request from a viewer (viewer request)
+ Before CloudFront forwards a request to the origin (origin request)
+ When CloudFront receives a response from the origin (origin response)
+ Before CloudFront returns the response to the viewer (viewer response)

If you're using AWS WAF, the Lambda@Edge viewer request is executed after any AWS WAF rules are applied.

For more information, see [Work with requests and responses](lambda-generating-http-responses.md) and [Lambda@Edge event structure](lambda-event-structure.md).