DjVu (pronounced "déjà vu") is a file format primarily designed for storing scanned documents, especially those containing text, photographs, and line art. It excels at compressing high-resolution images into relatively small file sizes, making it ideal for archiving and distributing documents online. DjVu achieves this compression through a combination of techniques, including wavelet-based image compression, separation of text and background layers, and lossy compression for the background and lossless compression for the text. This allows for clear and readable text even at high compression ratios. DjVu is often used for scanned books, manuals, and other documents where image quality and file size are important considerations. It supports features like searchable text, hyperlinks, and annotations, making it a versatile format for document management and distribution. While PDF has become more dominant, DjVu remains a viable option, particularly for older scanned documents or when extremely small file sizes are required.