As the title says. It would be great if the fluids for each barrel were only revealed after the representative liquid has actually been unlocked. I'm starting a new playthrough with a ton of new planets, and 90% of these barrels don't make sense to me lol.

That is outside the scope of this mod, but this one might address your concern: https://mods.factorio.com/mod/barrel-stages

Oh hot damn, I'll check that out!

Okay I checked it out, and now I'm unsure where the problem is. I'll create a thread there, but I'm guessing it doesn't support modded fluids or things like that. This mod wouldn't be doing anything that might influence that would it?

Nope, this mod only changes icons. Most likely that one doesn't support modded fluids, as you guessed

Hi, I will be merging @macintacos PR related to compat with other mods, but he also mentioned this mod here, and I am confused what it does. I tried enabling/disabling it and don't see a difference in barrel icons anywhere. Do you have a comparison/before-after picture of what it does and can you include that on the mod page?

See the thumbnail; it shows the contained fluid to the top left of the barrel icon.

I'm flattered, the icons must feel quite like vanilla :)

Good point on the comparison pic, will have to add that

Ah, now I see it after enabling/disabling it. Items on belts have the fluid icon as well. And it has an opt-in icon to swap barrel with fluid icon.