Yes, you can put aluminum foil in the oven. Aluminum foil is a common and safe material for cooking in the oven, as long as it is used correctly. It is often used to line baking sheets or roasting pans to prevent food from sticking, to wrap food for even cooking, or to create makeshift baking molds. Here are some important considerations when using aluminum foil in the oven:

1. Avoid direct contact with heating elements: Do not allow aluminum foil to come into direct contact with the oven’s heating elements, as this may damage the appliance or cause a fire. For example, some ovens have the heating element located under the floor. Placing aluminum foil on the bottom of the oven will reflect heat, causing uneven cooking or possibly damaging the heating element.
2. It’s best not to completely cover your oven racks: It’s best to avoid completely covering your oven racks with aluminum foil as it disrupts air circulation, which is essential for even cooking. Typically we cut the foil to size to fit the area where the food will be placed, leave some space between the foil and the edge of the shelf, and then place the food on top. However, based on feedback from many users, fully covering the oven racks for easier cleanup is a daily practice without any negative consequences. We seem to have become accustomed to using aluminum foil as the lining of our oven racks.
3. Proper ventilation: When using foil to cover food, be sure to leave some vents or use a loose tent to allow steam to escape. This helps food cook evenly and prevents excess moisture.
4. Use with non-acidic foods: When using aluminum foil in food, be careful with acidic foods like tomatoes or citrus, as they can cause the foil to degrade, causing the aluminum to leach into the food. While occasional use is generally considered safe, frequent consumption of food cooked in aluminum foil may pose health risks over time.
5. Oven-safe temperatures: Aluminum foil is generally safe to use at temperatures of 450°F (232°C). If the oven is too hot or the foil is in direct contact with the heating element, the foil may burn and produce smoke.
6. DO NOT USE IN MICROWAVE: Aluminum foil should not be used in microwave ovens as the metal can spark and cause a fire.

Be sure to refer to your specific oven’s manufacturer’s guidelines and foil packaging instructions; some manufacturers recommend not using aluminum foil in ovens (or certain parts of ovens, such as certain types of oven liners or trays) to ensure safe use. By following these tips, you can use aluminum foil effectively and safely in oven cooking.