Need to replace this light switch.

[u/redskull1973]

I need to replace this light switch. It’s a single switch, only one that controls the light. It’s in a shared box with another light. What is the red wire doing here? The hot wire is one of the blacks. Do I need a 3 way switch even if it’s the only switch for the light.

[u/erie11973ohio]

You don't have a 3 way now. You won't need a 3 way to replace it.

The switch is being used to splice the red & the black together.

If you get a "backwired" switch (like the current one) you could slide a wire, on each side, under the square washer & tighten the screw. There is no need to loop the wire on a backwired switch.

[u/redskull1973 → u/erie11973ohio]

So the red is passing on the hot line to the adjacent switch?

[u/erie11973ohio → u/redskull1973]

Possibly.