HEIF (High Efficiency Image File Format) is a flexible container format for individual images and image sequences. It uses modern compression algorithms like HEVC to store images more efficiently than traditional formats. HEIF separates the container format from the image encoding, meaning it can store images encoded with different standards, although HEVC is the most common. Sample HEIF files are used to test advanced image coding standards. Developers use them to verify support for features like auxiliary image items (depth maps, alpha channels) and image sequences (burst photos). They are also used to test the performance of decoders that need to handle complex container structures and metadata.