Zen Browser vs Firefox

Both Zen Browser and Firefox run on the same non-Chromium engine, so you're getting the same core tradeoff: fewer extensions, less reliable site compatibility, and a higher chance that websites won't work as expected compared to Chromium browsers.

Zen Browser tries to put a modern Arc-like spin on Firefox by adding features like a sidebar, but the review calls out that this doesn't solve the underlying problems. In fact, you'll notice even more friction if you're coming from Chrome or Safari, since only a tiny fraction of your extensions will work and you're more likely to hit bugs or missing developer tools. Unless you're already a die-hard Firefox fan who specifically wants a new look, you'll just run into the same extension and compatibility headaches, plus whatever quirks come from being built by a smaller team.

Firefox is the original here, and while it faces all the same ecosystem and compatibility issues, it's at least the source. If you want a privacy-focused browser that isn't Chromium-based, Firefox is the one to pick since Zen Browser doesn't actually fix or improve on the core limitations. Zen Browser is really just Firefox with a different coat of paint, and the review makes it clear you're better off sticking with Firefox if you're choosing between the two for this reason.