FlashPack is a new file format and loading mechanism for PyTorch that significantly speeds up model checkpoint loading, achieving 3-6 times faster performance than existing methods. By flattening weights into a contiguous byte stream and optimizing parallel processing between CPU and GPU, FlashPack enhances efficiency in model I/O, making it ideal for machine learning applications. Users can easily convert and integrate their models with FlashPack to benefit from faster loading times.