Freeze plugs

You may find this hard to believe, but we can't see it over a computer. The heater core could be leaking. You'd see the puddle to the right of and behind the right front tire. A core plug could be corroded. Radiator could be corroded.

If you can't tell where the coolant is leaking from, you can add a small bottle of dye to it. Drive a few miles long enough to get the engine warmed up, then search with a black light. The dye will show up as a bright yellow stain that you can follow back to the source.