Firefox mostly, but I use Chrome for some things and mostly development.
I do want to add though that it's almost comical how the browser market has flipped. It went from massively dominant Internet Explorer to massively dominant Chrome, and for the same reason: major monopolies using their power to push their product. Unfortunately the downside is that Google is in the business of your information, which is worse than Microsoft ever was. This also presents a problem for web developers, because an increasing number of them only test on Chrome, and that causes some websites to not display/function properly on Firefox/Safari, and users end up loading up those browsers, getting broken websites, and blaming the browser instead. It's not even their fault, and they have been reduced to having teams of developers go over websites reported to them that fail to render properly and
change their browser to fix lazy web developers problems instead. This is terrible for the internet. The entire reason the internet became so popular is arguably because it was decentralized and few regulations allowed ideas and websites to flourish. But allowing one profit-driven corporation to corner the entire browser market is bad news bears. It's even worse now that Google is increasingly flouting its #1 status to change the internet to work better for Google instead of the people, such as forcing web developers to
create two versions of their websites so Google can cache it using its AMP service. They 'force' developers to do this by de-prioritizing non-AMP sites.
Here are some statistics on browsers from W3:
Ironically, as I stated before, Google has come to dominate the browser market the same way Microsoft did, and Microsoft got hit with antitrust violations for that. Google should face the same fate. Turns out bundling browsers with operating systems isn't as important anymore as effectively bundling browsers with search engines, which is what Google did to gain such dominance in the first place. Google needs to be taken down a notch before they swallow even more of the internet.