Amazon CloudFront
Developer Guide (API Version 2016-09-29)

HTTP 503 Status Code (Service Unavailable)

An HTTP 503 status code (Service Unavailable) typically indicates a performance issue on the origin server. In rare cases, it indicates that CloudFront temporarily can't satisfy a request because of limited resources at an edge location.


If you're a customer trying to access a website or application, and you've gotten this error, there's probably just unusually high traffic to the site. Please wait a little while, and then try accessing the site (or running the application) again. If you still get an error, please contact the website or application distributor directly for support.

Why is this error coming from CloudFront? CloudFront helps websites speed up delivery of content, like images or web pages, to customers by storing copies in servers located around the world. But when there's a lot of internet traffic to a website and the site can't keep up, an error is returned when anyone tries to access the site. When CloudFront can't access content that you've requested from a website, it passes on the error from the site or application that you're trying to use.

Origin Server Does Not Have Enough Capacity to Support the Request Rate

CloudFront generates this error when the origin server is overwhelmed with incoming requests. CloudFront then relays the error back to the user. To resolve this issue, try the following solutions:

  • If you use Amazon S3 as your origin server, optimize the performance of Amazon S3 by following the best practices for key naming. For more information, see Request Rate and Performance Considerations in the Amazon Simple Storage Service Developer Guide.

  • If you use Elastic Load Balancing as your origin server, see 503 Error Classic.

  • If you use a custom origin, examine the application logs to ensure that your origin has sufficient resources, such as memory, CPU, and disk size. If you use Amazon EC2 as the backend, make sure that the instance type has the appropriate resources to fulfill the incoming requests. For more information, see Instance Types in the Amazon EC2 User Guide for Linux Instances.

CloudFront Caused the Error Due to Limited Resources at the Edge Location

You will receive this error in the rare situation that CloudFront can't route requests to the next best available edge location, and so can't satisfy a request. This error is common when you perform load testing on your CloudFront distribution. To help prevent this, follow the Load Testing CloudFront guidelines for avoiding 503 (Capacity Exceeded) errors.

If this happens in your production environment, contact AWS Support.