The .afpub file extension is the native file format used by Affinity Publisher, a professional desktop publishing software developed by Serif. This format is designed to store complex page layouts, including text, vector graphics, raster images, and typography settings, all within a single project file. Unlike flattened formats such as PDF, an .afpub file maintains all editable layers, non-destructive adjustments, linked assets, and master page configurations, allowing designers to revisit and modify every element of their publication at any time. It is built on a modern, high-performance engine that supports advanced features like CMYK color management, professional-grade pre-press tools, and complex text wrapping. Because it is a proprietary format, it is optimized specifically for the Affinity suite's workflow, ensuring seamless integration when moving assets between Affinity Designer and Affinity Photo. The format is widely used by graphic designers, print professionals, and publishers for creating brochures, magazines, books, and marketing materials that require high-precision layout control and professional output capabilities.