alt Hacker NewsPSA for those who aren’t aware: Chromium/Firefox-based browsers have a Network tab in the developer tools where you can dial down your bandwidth to simulate a slower 3G or 4G connection.
Combined with CPU throttling, it's a decent sanity check to see how well your site will perform on more modest setups.
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I still test mine on GPRS, because my website should work fine in the Berlin U-Bahn. I also spent a lot of time working from hotels and busses with bad internet, so I care about that stuff.
Developers really ought to test such things better.
CPU/network throttling needs to be set for the product manager and management - that's the only way you might see real change.
We have some egregious slowness in our app that only shows up for our largest customers in production but none of our organizations in development have that much data. I created a load testing organization and keep considering adding management to it so they implicitly get the idea that fixing the slowness is important.
It doesn't throttle Websockets, so be careful with that
For macOS users you can download the Network Link Conditioner preference pane (it still works in the System Settings app) to do this system wide. I think it's in the "Additional Tools for Xcode" download.
This made me chuckle.
I had a fairly large supplier that was so proud that they implemented a functionality that deliberately (in their JS) slows down reactions from http responses. So that they can showcase all the UI touches like progress bars and spinning circles. It was an option in system settings you could turn on globally.
My mind was blown, are they not aware of F12 in any major browser? They were not, it seems. After I quietly asked about that, they removed the whole thing equally quietly and never spoke of it again. It's still in release notes, though.
It was like 2 years ago, so browsers could do that for 10-14 years (depending how you count).
For Firefox users, here's where it's hidden (and it really is hidden): Hamburger menu -> More tools -> Web developer tools, then keep clicking on the ">>" until the Network tab appears, then scroll over on about the third menu bar down until you see "No throttling", that's a combobox that lets you set the speed you want.
Alternatively, run uBlock Origin and NoScript and you probably won't need it.
I once spent around an hour optimizing a feature because it felt slow - turns out that the slower simulated connection had just stayed enabled after a restart (can’t remember if it was just the browser or the OS, but I previously needed it and then later just forgot to turn it off). Good times, useful feature though!