Skip extension cords without a UL mark.

Yes, they differ — and the difference is that non-listed cords often lie about their ratings. A UL-listed cord has been tested to safely handle the amps and volts printed on it. A no-name cord from a discount bin might claim 15 amps but actually use 18-gauge wire that will overheat way before that.

UL (or ETL, CSA — same idea) means an independent lab verified the cord’s gauge, insulation, and plugs can actually do what the label says. Without that, the manufacturer just printed numbers that look good. I’ve cut open cheap cords and found wire thinner than the packaging suggested.

This is not a spec you guess on. An underrated cord under load gets hot, melts, and starts fires. Pay the extra few bucks for the UL mark — or buy from a brand like Coleman Cable or Southwire that lists their testing clearly.

Trust the sticker, not the price tag.