A door closer is a mechanical device installed at the top or inside a door to ensure it closes automatically after being opened. Commonly used in commercial buildings, offices, and residential spaces, it enhances safety, security, and energy efficiency. By controlling the speed and force of closing, a door closer prevents slamming, reduces noise, and minimizes wear on hinges and frames. It is especially important for fire-rated doors, helping maintain proper sealing and compliance with building safety regulations.