Easy Image Optimizer (ExactDN) and Amazon S3
Both Easy Image Optimizer and the ExactDN service can operate automatically with images stored in an S3 bucket.
Both virtual-hosted and path-style rewriting is supported:
Buckets with a period (.) in the name cannot use virtual-hosted urls with secure HTTPS requests. This is because the AWS security certificates can only cover 1 level of sub-domains under s3.amazonaws.com.
However, all region specific domains, like s3-us-west-2.amazonaws.com will also work properly with ExactDN.
Automatic configuration is only supported with WP Offload Media, if you use a different S3 plugin, you will need to manually configure the "local" domain, like so:
define( 'EXACTDN_LOCAL_DOMAIN', 'https://s3.amazonaws.com/bucket-name/' );
The preview URL shown by the WP Offload Media plugin contains non-breaking dashes that are not actually valid URL characters. As a result, you should not use copy & paste to enter your S3 domain/address on the Manage Sites page. Type the url in manually, and it will work just fine.