Now combine the above with the fact that i'm using a ~23" 1366x768 monitor, the tendency of pretty much every site out there to use the window width as a means to differentiate between mobile and desktop sites and the stupid trend to use ginormous font sizes everywhere and you get an idea of how much i like browsing many sites out there (at least HN and old Reddit is perfectly fine). Well, i'm thankful that browsers have a zoom option at least, many of the sites out there are only usable at a 70-80% zoom for me.
But yeah, last time i had my browser maximized all the time was when i had a 4:3 monitor.
It's time to upgrade.
This is a brand new monitor i bought some months ago (late 2019) and the cost was much bigger than 5 dollars. In fact it was the most expensive VA monitor at this resolution (i avoid IPS because i actually want to be able to see dark colors and contrast and every single IPS monitor i've used, regardless of resolution, is garbage when it comes to that with the awful backlight glow), it has a ton of inputs at the back, relatively fast response time (for VA), etc. It is one of the best monitors i ever had.
The resolution was something i explicitly opted for, partly because at the time i had an APU-based system that i wanted to game on and i didn't want the blurry mess that a higher resolution would have and partly because 1366x768 on a monitor (as opposed to laptop) makes for very sharp icons, fonts (after you disable antialiasing) for everything (as opposed to using a hidpi monitor where some apps look crisp and others look either too tiny or blurred from scaling). Also as a (very high) bonus, it looks great when playing older games that often use 1024x768 as a resolution since i have 1:1 mapping there.
Finally 1366x768 is currently by far the most common resolution on PCs (mainly thanks to laptops, but desktops use it too - see mine) according to statcounter and the second most common on gaming PCs according to Steam, so it isn't something you'd only find in obscure old PCs, it is as mainstream as it gets.
How would you differentiate them? At least with the width you can use css media queries so no Javascript is needed.
Not sure, i'm not into web development, i just see using the window width as the wrong way. I keep my window down to that size even when i'm using monitors with larger resolutions (1080p or 1440p), it is a bad idea to assume window width == monitor resolution == device type.
Although in the case of Reddit the old design isn't perfect either, because if the browser window is narrow enough it'll have a bug where you can shift the whole website out of the visible area by writing a long line in a comment.
To be clear, I know this is not a trivial thing, but when UI designers don't know how to handle certain viewport sizes they should rather just let the browser's scrollbars do the job they've been doing fine for decades.