My guess, as someone who doesn’t know the answer but works closely in this field, is that the potential downside (i.e. privacy/security) was much greater than the actualised benefit (i.e. performance).
Safari (who make a big deal about being privacy-conscious) was the first to introduce cache partitioning, looking into it as far back as 2013[1]; Chrome followed in 2020 and Firefox in 2021[3]. One thing I know, anecdotally, to be a strong motivator among browser vendors is ‘X is doing it, why aren’t we?’
You are correct that this is an optimisation only available to H2+, but optimising to the H/1.x use-case is a use-case not worth optimising for—if one cared about web performance that much, they wouldn’t be running H1/.x in the first place.
> if one cared about web performance that much, they wouldn’t be running H1/.x in the first place.
You may not have intended it this way but this statement very much reads as "just use Chrome". There's lots of microbrowsers in the world generating link previews, users stuck with proxies, web spiders, and people stuck with old browsers that don't necessarily have H2 connectivity.
That doesn't mean over-optimize for HTTP 1.x but decent performance in that case should not be ignored. If you can make HTTP 1.x performant then H2 connections will be as well by default.
Far too many pages download gobs of unnecessary resources just because they didn't bother tree shaking and minifying resources. Huge populations of web users at any given moment are stuck on 2G and 3G equivalent connections. Depending where I am in town my 5G phone can barely manage to load the typical news website because of poor signal quality.
Regarding the resource hijacking (security vulnerability) risk, one need not just imagine it anymore. It actually happened, a few years after your blog post was written: https://news.ycombinator.com/item?id=40791829
I vividly remember this happening. Firstly, because I was an affected customer and I had to cancel all of my debit/credit cards days before a two-week work trip to SF, but secondly…
I was approached by BA to tender for a web performance project. I was excited because, at the time, I had Gold status with BA and I used the site on a weekly basis—I knew exactly where and why it was slow simply through using it so much!
The RFP deadline was short—really short. So, I spent the bulk of a vacation in Croatia writing up my proposal. When I was meant to be lounging by the pool or chugging Malvasia, I was buried in my laptop putting together my pitch. I got it done in time, fired it over, only to be told ‘we are focusing on web security now; this project is on hold’. Then, a few days later, the news broke.
Hugely instrumental in my career. Landed me my first ever job (2008) and has been responsible for underpinning most of my consultancy career (2013–now): https://csswizardry.com/
As long as one sticks with it, I cannot overstate the power of a good personal website.
> Also I can't decide what to write about, and whether to make it more nerdy or more professional.
As with most decisions, just make one. You can always change your mind later.
