[varenc]

fun fact: source maps are used by some Tor onion sites ("dark net") as part of a captcha process without using JavaScript. If you present the user with an image, and ask them to click on a particular part of it, the server can recieve exactly where they clicked and validate if that's correct without using JS at all. (JS is a big no-no on Tor hidden network sites)

[40four]

That actually makes a lot of sense, and it helps me wrap my head around why the technique exists at all. As someone who didn’t get into web programming until 2015 or so, I didn’t quite understand at first the usefulness of this. But for sites like this built in the 90’s it was a totally different world

[varenc]

The way source maps are used by dark net sites, and the reason it exists, are probably unrelated! I think it was just an early form of using image tiling for big efficiency gains. Now with HTTP2/QUIC you can request many small individual images without much overhead, but back the day there were huge gains by sending one larger image instead of 50 smaller ones. (There's also the pure CSS solution used with image sprites that's between the old web and the current era, but I digress)

[hdjrudni]

There's probably some efficiency to it too. Encoding a dozen images as one and load them in one request will be quicker than 12 separate images each with their own overhead.