Copic markers are, broadly speaking, oil-based markers. However, many definitions of oil-based markers mention the use of strong organic solvents, and since our inks mostly consist of alcohol, we prefer calling Copic markers alcohol-based.

What kind of alcohol is in Copic markers?

Let me be VERY clear: I would never, EVER put rubbing alcohol (isopropyl alcohol) into my Copic markers, which are ethanol-based.

Can you use alcohol markers on watercolor paper?

You have to know that not all papers are compatible with alcohol marker's ink. Some papers, like watercolor paper, tend to absorb a lot of ink, their granulated texture could also damage your marker's nib. Marker paper, Smooth Bristol or even Mixed media paper is, on the other hand, better to use with alcohol ink .