What does this mean in practice?

The native output is 720p. If you need 4K, use a post-process video upscaler (e.g., Topaz Video AI or Real-ESRGAN for video). Do not try to generate higher than 720p natively; the model will collapse.

The file is a high-performance, open-source model used for Image-to-Video (I2V) generation. Developed by Alibaba's Wan-AI, it is part of the Wan 2.1 suite and is specifically designed to transform static images into high-definition, 720p video clips. Key Specifications