Web, backend, mobile are the big ones. If you're after money, avoid: embedded, graphics, scientific, math-based, systems programming (aka the interesting ones).<p>Also, maybe it's anecdotal, but amongst my peers, its the devops folks who are currently getting most money. Might be because everybody is transitioning to cloud and there's a shortage of people who know how to set it up.
I'm doing native Android development. My salary alone is well above the median <i>household income</i> for the most expensive district. If I had qualified for a couple of remote jobs I interviewed for, a single person salary would be well within the top 5% of household income.<p>It may not be the highest, but it is a good amount of money.<p>Native iOS development pays a little better, though.
I think the real answer here in terms of long term career "scaling" and upward mobility is to work in product with prior experience in engineering. Clearly unless you're brilliant or credentialed enough to eventually be a principal engineer, the engineering side is a never ending treadmill with a glass ceiling that emerges way earlier than most would think.