SR3 is a diffusion-based super-resolution model that enhances low-resolution images through iterative denoising. Starting from pure Gaussian noise, the model progressively refines the image using a U-Net architecture trained to denoise at various noise levels. This approach enables the generation of high-fidelity images across various magnification factors, including 4×, 8×, and 16×, particularly excelling in face and natural image super-resolution tasks. The implementation is provided in PyTorch.