This page demonstrates how Encore observes Web filtering using cross-origin embedding. It embeds two images, one that is filtered and one that is not. Using the onload and onerror events, we detect whether each image successfully loaded from the remote origin and set the contents of the boxes below each image.
For purposes of demonstration only, the filtered image is actually a nonexistent image rather than an image blocked by actual Web filtering. This lets the demo work for users in countries that don't experience Internet censorship.