I've noticed that both Firefox and Chrome issue a new HTTP request when you view the source for a web page that you've already loaded. It's particularly annoying when the page itself is slow to load or if it won't load at all.
Why is that? Wouldn't they have the existing source for the originally received page cached already? Is it based on Cache-Control headers?
This has been on my mind for a while (usually, comes up when looking at what's behind slow web apps).
In the context of Chrome, according to this link it is indeed base on Cache-Control headers.
...view-source grabs the html source from the http cache and pretty-prints it, but for the page NOT in http cache, it's 'forced to' make a new request.
To me, this makes sense. You wouldn't want to use what is currently rendered as the source of truth as obviously the HTML can be manipulated dynamically. If you can't use this, then the http cache would be the next likely candidate for the source. If the source in unavailable from cahce, a subsequent GET of the source seems to be the only alternative.
This does, however, introduce another interesting delima raised here.
Requesting the URL again doesn't make sense as there is no guarantee that source received during the second request will match what was received during the first request.
I would imagine this was a conscious trade-off that was made to ensure that a view-source request is always satisfied in some form or another.
