Is a 50-foot 12-gauge extension cord safe for a refrigerator?

Yes, it should work without damaging the compressor. A refrigerator typically draws 6–10 amps, and a 12-gauge cord at 50 feet will have a voltage drop of less than 2% — well within safe range. Make sure the cord is rated for outdoor use if in a garage, and don’t coil the extra length tightly.