GDSII (Graphic Data System II) is the standard binary file format for storing IC layout data — representing the physical design as a hierarchical collection of polygons, paths, and references organized in cells (structures), used for design interchange between EDA tools, foundries, and mask shops.

GDSII Format Details

• Hierarchy: Designs are organized as cells (structures) that can reference (instantiate) other cells — compact representation.
• Geometric Elements: Boundaries (polygons), paths (lines with width), text, and structure references (instances).
• Grid: All coordinates are on a fixed grid — typically 1nm or 0.5nm database unit.
• Layers/Datatypes: Features are organized by layer number and datatype — encoding different process layers.

Why It Matters

• Industry Standard: GDSII has been the IC industry standard since the 1980s — universally supported.
• Limitations: 32-bit coordinates, 2GB file size limit, no curved elements — increasingly constraining for advanced nodes.
• Replacement: OASIS (Open Artwork System Interchange Standard) addresses GDSII's limitations for advanced designs.

GDSII is the lingua franca of chip design — the universal IC layout format that connects design tools, foundries, and mask shops.