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

Adding and Accessing Content That CloudFront Distributes

When you want CloudFront to distribute content (objects), you add files to one of the origins that you specified for the distribution, and you expose a CloudFront link to the files. A CloudFront edge location doesn't fetch the new files from an origin until the edge location receives viewer requests for them. For more information, see How CloudFront Delivers Content.

When you add a file that you want CloudFront to distribute, make sure that you add it to one of the Amazon S3 buckets specified in your distribution or, for a custom origin, to a directory in the specified domain. In addition, confirm that the path pattern in the applicable cache behavior sends requests to the correct origin.

For example, suppose the path pattern for a cache behavior is *.html. If you don't have any other cache behaviors configured to forward requests to that origin, CloudFront will only forward *.html files. In this scenario, for example, CloudFront will never distribute .jpg files that you upload to the origin, because you haven't created a cache behavior that includes .jpg files.

CloudFront servers don't determine the MIME type for the objects that they serve. When you upload a file to your origin, we recommend that you set the Content-Type header field for it.