>A couple of weeks back, I was using a family member's Spectrum “high-speed” cable modem service at a whopping 5Mbps with latency measured in the hundreds of milliseconds.

And that's still great internet compared to some places. I have a house out in the middle of nowhere that is only served by a single satellite internet provider (surrounded by trees that block the view to other providers' sats). I get 20Mbs at ~500-1000ms latency for a few days before I hit the 20Gb cap, then I get 0.5-1Mbs for the rest of the month. Hacker News is one of the few sites on the web that I can browse relatively painlessly when I'm up here.

A couple of years back I was at a conference in Rome. Literally in the heart of the city (the windows overlooked the Forum) and that meant that they had only satellite access because nobody had run cables through the historic buildings. I've never been more glad to have spent time optimizing our site for 2.5-3G performance than when we were demoing it during presentations and it seemed slow but almost everything else was unusable.

I'd put network use in a different category. It is an important issue though.

Thankfully the tools are getting better for this. The recently supported font-display property is a great one. It allows devs to choose how to handle web font rendering over slower internet connections.

Now I just wish more devs would start to take advantage of all the great performance tools available. Those best practices are unfortunately rarely taught.

> I'd put network use in a different category. It is an important issue though.

My rationale for considering it to be included is that as the concept was developed I took the spirit of progressive enhancement to be doing the best with what your users have rather than only catering to people with the same setup you have.

> Now I just wish more devs would start to take advantage of all the great performance tools available. Those best practices are unfortunately rarely taught.

Agreed. I think one of the challenges has been both showing business value from performance — once you're putting things into a cost/benefit comparison it's a lot easier to get people to routinely consider the performance impact of their decisions.

for font-display, do you prefer swap or fallback?

It might depend on main body text versus title text. It's jarring when body text changes so I'd prefer fallback in that case. For a title which might have more branding concerns, I'd prefer swap.