It's the only page you can read on a GPRS connection (http) and you can literally see every packet as it's transmitted, because the page is rendered bit by bit.
Presumably he's talking about incremental rendering[1], though I couldn't get it to work on Fefes Blog by manually throttling using the dev tools.
It's pure, unstyled HTML -- you could read the site by piping curl into less -- and it should easily render incrementally; I'm just not sure how well it works when you use gzip and TLS (and I couldn't not use TLS when I just tried).
Is there a way to slow it down on fast connections and or a video of this? I have an academic interest and am curious how they did this, but don't have an easy way to demonstrate it to myself as I don't currently have a connection slow enough that it doesn't render instantaneously.
Both Firefox[1] and Chrome[2] (and, presumably, Safari and Edge?) have a network throttle in their dev tools. Apart from that, you can use OS level throttling, e.g. Network Link Conditioner[3] for OS X. Couldn't see any incremental rendering on Fefes Blog though.
It's the only page you can read on a GPRS connection (http) and you can literally see every packet as it's transmitted, because the page is rendered bit by bit.