An alias in API Gateway holds environment-specific property values that can be used in policy routing configuration. The aliases can be referred to in routing endpoints, routing rules, endpoint connection properties, outbound authentication tokens, and outbound HTTP headers instead of providing a real value. The corresponding alias value is substituted in place of an alias name during run-time. Thus the same alias can be referred to in multiple policies and the change in a particular alias would affect all the policy properties in which it is being referred. When an API is exported and imported to a different environment, you can update the alias values specific to the environment instead of updating the policy with environment specific values. You can create four types of alias: