Yes, it is safe to leave a plug in an outlet, even if the appliance is not in use. Modern outlets are designed to supply power continuously without causing overheating or other issues.

Leaving a plug in the outlet can even be convenient, as it allows you to easily connect the appliance when you want to use it. However, it is important to take some precautions:

1. Ensure that the plug fits securely in the outlet and there are no loose connections. A loose plug can cause overheating and pose a fire hazard.

2. Regularly check the condition of the plug and the cord. If you notice signs of damage, such as worn insulation or exposed wires, unplug and replace it if necessary.

3. If you do not use an appliance for an extended period, such as during vacations, you might choose to unplug it from the outlet to save energy and reduce the risk of any electrical issues.

It is important to be aware of safety and regularly inspect the condition of plugs and outlets to avoid potential risks.