[chronial]

> Why would I care about the other cases?

Because you talk about the other cases when you make general statements like:

> it's that FireFox just isn't as fast as Edge.

> I can't change my code,

I wasn't suggesting you change anything about your code. Remember, the context of this conversation is this Statement by GP:

> I hate that I know exactly why. It's because they were only ever tested on Chrome during development.

The reality is that Firefox has a tiny market share at this point, so it is questionable how much time should be invested into optimizing pages to make them fast on Firefox. But that is a problem with Firefox's market position, not technology.

My point was that when code is slow in Chrome, you change it and never notice whether Firefox would have been faster in those cases. You only test code that is sufficiently fast in Chrome in Firefox. Thus, you don't usually see the cases where Firefox is faster than Chrome.

[jodrellblank]

The context from the GP is relevant, my reply was to say no don't accuse laziness and ignorance, I do use FireFox as my daily browser, I did test with FireFox, I wanted my page to be equally good and I couldn't achieve that. The effort of rewriting to get 'great' responsiveness in Edge got 'sub-par' in FireFox - and it's not because I didn't bother trying.

Your last paragraph is probably true in general, and true specifically for me because the Windows server I was using had Edge and didn't have Chrome or FireFox.