Outdoor cords are more than just a tougher jacket.

Yes, the jacket is the most obvious difference, but the internal wiring and features matter too. Outdoor extension cords use heavier gauge wire (lower AWG) to handle longer distances without voltage drop, have molded or sealed plugs to keep moisture out, and are almost always grounded (three-prong). Indoor cords often use smaller gauge wire, are ungrounded, and lack any moisture protection.

The jacket material itself is different — indoor cords use PVC that gets brittle in cold and degrades in UV. Outdoor cords use rubber or heavy vinyl that stays flexible and resists weather. But don’t just look at the jacket: if it’s rated for “indoor use only,” it’s not built for outdoor loads, moisture, or temperature extremes.

Using an indoor cord outside is a short circuit waiting to happen. If it’s going outside, spend the extra few bucks on a proper outdoor cord.