Do you know a webpage appearance comparator?

Question

I need a tool to compare the design of a website, I do not want to compare the HTML code only, but the output design.

Is this even possible? also is there any openso

Answer 1

I'm working on one and i tell you it's hard and there is nothing on the market. Maybe Google and Bing have something inhouse. You can use some image comparison tools which identify rectangle regions of changed images. This is for example a part of all modern video compression but you have to do it for different regions of the webpage (the nav bar section, the main article, the region filtered by an ad-blocker etc.) as some of them may change and it's still considered the same content on the page.

As i said very complex problem with no exact solution.

The other is going the non visual way and just compare the resulting computed computer styles of each html element. You have to hack the browser to get access to the layout tree. There is also no official API or existing library/program/hack/patch for it.