The Gerber Layer Format Specification, Revision 2026.05
The normative description of the current Gerber layer format, including geometry, metadata attributes, drill and rout data, CAD netlist semantics, component data, errors, and deprecated constructs.
Gerber is an open, human-readable 2D vector image format used as a de facto standard for PCB fabrication data. Revision 2026.05 defines not only image primitives but also attributes that identify file function, apertures, pads, nets, components, drill and rout features, and assembly information.
Practical contribution #
The specification makes a crucial distinction between geometry and intent. Geometry says which region is copper, mask, paste, or profile. Attributes can say which physical layer a file represents, whether a flash is a component pad or via, what net it belongs to, and which component owns it. That semantic context enables stronger automated checks and less ambiguous communication.
The specification also covers:
- coordinate format, units, interpolation, arcs, apertures, regions, step-and-repeat, transformations, and numerical accuracy;
- file, aperture, and object attributes;
- PCB fabrication and assembly data, including drill/rout, CAD netlist, and component information;
- error conditions, bad practices, and deprecated constructs such as Standard Gerber/RS-274-D.
The production lesson is not “export Gerbers and send them.” It is to release a self-consistent, versioned data package and inspect the exported result in an independent viewer. The native CAD database and the released package are different configuration items.
Visual audit #
All 219 pages were inspected. The information-bearing visuals are precise geometry examples: aperture construction, region filling, block and step/repeat behavior, attribute relationships, drill maps, component footprints, and examples of malformed or deprecated data. They are excellent normative test cases but too syntax-specific for a conceptual GTK chapter. No figure is copied. The topic entry instead uses a package-level data-flow diagram; readers who implement a parser or generator should consult the archived specification directly.
Limits #
Gerber defines a data format, not a complete fabrication contract. Stackup, materials, tolerances, finish, impedance requirements, acceptance class, panelization agreement, assembly drawings, BOM, placement data, and change authority still require controlled documentation. Gerber attributes reduce ambiguity but do not repair inconsistent source design data.