FOSS4G 2023 Prizren SOZip (Seek-Optimized ZIP) is a new open specification on top of the ZIP archive format to compress one or several files organized and annotated such that a SOZip-aware reader can perform very fast random access (seek) within a compressed file. SOZip makes it possible to access large compressed files directly from a .zip file without prior decompression. It is not a new file format, but a profile of the existing ZIP format, done in a fully backward compatible way. ZIP readers that are non-SOZip aware can read a SOZip-enabled file normally and ignore the extended features that support efficient seek capability. We will present how SOZip works under the hood and discuss about SOZip implementations, in particular in GDAL, which make it possible for its downstream users, in particular QGIS, to read seamlessly and efficiently large compressed files in GeoPackage, FlatGeoBuf, or shapefile formats.