Thank you for the suggestion! It uses 1024x1030 if I recall correctly as a viewport.

What I was thinking about is showing the generated screenshot after "Start" and then giving an option to upload your own screenshot instead if the current one doesn't work well. What do you think about it?

I like how simple and easy it is, perhaps if you just load the website in an iFrame below for "desktop" loading, and then show images for the smaller view ports? IE: I see a lot of value in doing iPhone/mobile based viewports and providing a qrcode so we can load quickly on our own devices if wanting to test further.

Also - I've found that in some cases it's hard to tell if they want just an individual page critiqued or an entire website - perhaps something needs to be done to clarify this?

_Excellent_ suggestions, thank you!