Reheat cooled fried foods on a wire rack in a preheated oven at 200°C / 390°F for 5–10 minutes, or in an air fryer at 180–190°C / 355–375°F for 3–5 minutes, to crisp them again. A microwave softens fried foods because it heats the water inside the food, and that moisture moves into the crust. Reheat fried meat and poultry until the thickest part reaches 74°C / 165°F.
Fried food softens as it cools because moisture inside gradually moves toward the crust, and the dry crust absorbs it and becomes flexible. This change goes further when fried food sits in the refrigerator. To crisp it again, the moisture in the crust needs to evaporate, which takes dry, high heat. An oven and an air fryer dry the crust from the outside with hot, dry air; a microwave heats the food from the inside, turns water into steam, and lets that steam pass through the crust, making it even wetter. Fried food stored in a covered container in the refrigerator softens for the same reason.
The most reliable method is the oven. Preheat it to 200°C / 390°F; fried food placed in a cold oven heats slowly and dries out. Arrange the pieces in a single layer with space between them on a wire rack set over a sheet pan; pieces placed directly on the pan stay soft underneath. Reheat french fries and thin pieces for 5–10 minutes, and breaded chicken and thicker pieces for 10–15 minutes. Turn the pieces once halfway through. If needed, line the pan beneath the rack with parchment paper. After reheating, leave the pieces on the rack for a minute or two so the remaining steam can escape.
An air fryer is faster for small amounts. Preheat the basket for a few minutes, arrange the fried foods in a single layer, and reheat them at 180–190°C / 355–375°F for 3–5 minutes; shake the basket halfway through. If the basket is overfilled, the pieces on the bottom soften in the steam from the others. A skillet also works: heat a nonstick or cast-iron skillet over medium heat, then reheat the fried foods for a few minutes, turning them occasionally, with no added oil or just a few drops. Do not cover the skillet; the lid traps steam inside.
The best way to revive french fries is to fry them briefly again. Dipping cold fries into oil at 180°C / 355°F for a few minutes brings them close to their original crispness. Old oil and sauce residue on the surface may burn during reheating, so remove sauce from sauced or mayonnaise-coated fried foods before reheating. Taste reheated fried food before adding salt; the original salt may still be enough.
Food safety matters, too. Refrigerate fried foods within two hours of cooking and eat them within three to four days. When reheating fried chicken, meat, or fish, heat the inside as well as the crust; the thickest part should reach 74°C / 165°F. With thick pieces, the crust heats before the inside and may start to burn; if that happens, lower the oven temperature slightly and extend the time. Do not cool and reheat a portion a second time.