Glossary comparison
DEF vs LEF: what is the difference?
The difference
LEF describes the library: layers, vias and the outline and pins of each cell. DEF describes one design built from that library. Each needs the other.
DEF, the Design Exchange Format, describes one design: its constraints, layout and netlist, including placed instances and routing. LEF describes the library and technology that the design uses.
The two terms
DEF
An ASCII format that captures the physical state of a specific design: die and core area, component placement, net connectivity, routing geometry, pins, blockages and special nets.
LEF
An ASCII format describing the physical abstract of library cells and macros: outline, pin shapes and layers, obstructions and antenna data. Place and route tools read LEF instead of full GDSII geometry to keep the design database tractable.
Side by side
| Field | DEF | LEF |
|---|---|---|
| Stands for | Design Exchange Format | Library Exchange Format |
| Type | Standard | Standard |
| Domain | EDA Tools & Flows | EDA Tools & Flows |
| Group | Design data formats | Design data formats |