Back in 2009, Digg started wrapping external links on their site in an
iframe using a URL shortener. The “DiggBar”, as it was called, was widely derided for, among other things, stealing search rankings — this was back when Digg was relevant — and breaking bookmarking. It was adjusted shortly after launching, only to be killed off about a year later.
So, lesson learned, right? Well, not as far as Google is concerned. Alex Kras enabled AMP on his self-hosted WordPress site, only to find it ruined his URLs:
Most importantly, I was surprised to find out that instead of redirecting users to an optimized version hosted on my server, Google was actually serving a snapshot of the page from their own cache. To make things worse, Google was injecting a large toolbar at the top of the snapshot encouraging users to get back to Google search results (a functionality already provided by the back button) and making it harder to get to the original site.
A while back, I was trying to get access to the regular version of a page because there was an element that was broken on the AMP version. To do so, I had to adjust the URL manually — there appeared to be no other way to get to the HTML page.