When uploading images to Cloudinary, instead of uploading the actual image files to Cloudinary, you can also specify a remote HTTP URL of existing images. This method allows for a much faster uploading. You can also specify an S3 URL of an existing image. The S3 URL should be of whitelisted S3 buckets we define for your Cloudinary account. This way you can upload images to Cloudinary directly from an existing S3 bucket and then dynamically deliver transformed and resized versions to your users via a fast CDN.
More information regarding uploading to Cloudinary in the following link: http://cloudinary.com/documentation/upload_images
Another option is to use Cloudinary's 'fetch' URL for transforming and delivering remote images on the fly, as explained here.
Lazy migration of your assets from a remote URL or S3 bucket is also possible.
More information can be read on this documentation page.
We support whitelisting S3 buckets in the US standard zone (us-east-1).
If you have a EU S3 bucket you can upload from the HTTP URLs without the need of whitelisting your bucket. Also note that we do support whitelisting EU S3 buckets whitelisting, however this requires custom manual setup on our side, specifically per account, therefore this is offered for our Advanced plan onward.