The short answer
Gerber X2 describes PCB fabrication images and adds machine-readable attributes that explain what files and image objects represent.
Gerber X3 extends this attribute-based format with dedicated component layers that carry component placement and assembly information.
X3 does not discard X2. It builds on the same Gerber language and complements the fabrication data with assembly data.
From graphical images to richer manufacturing data
Gerber has long been used to transfer PCB layer images such as copper, solder mask, legend and paste. Traditional Gerber data accurately describes the geometry that must be manufactured, but filenames and separate documentation were often needed to explain the purpose of each file and feature.
Attributes add standardized metadata without changing the plotted image. A viewer that does not interpret the attributes can still render the geometry, while compatible software can use the additional information to understand the designer's intent.
Gerber X2
PCB fabrication images plus standardized file, aperture and object attributes.
Gerber X3
The X2 foundation plus component layers for PCB assembly information.
What is Gerber X2?
Gerber X2 was introduced by Ucamco in 2013. It added a standardized attribute system to the existing Gerber format. These attributes provide information about the file as a whole, the apertures used to create objects and individual graphical objects.
File attributes
Describe the role of the file, such as whether it represents top copper, bottom solder mask, a profile or another manufacturing layer.
Aperture attributes
Describe the intended function of apertures and the objects they create, such as conductor, SMD pad, via pad or fiducial.
Object attributes
Can associate image objects with net names, component references and pin numbers when the exporting software includes that information.
Backward-compatible images
The attributes do not alter the image. Software that ignores them can still display the intended Gerber geometry.
X2 already supports component-pin-net relationships
It is a common oversimplification to say that X3 introduces all net and pin data. X2 object attributes can already identify a net, component reference and pin for fabrication objects. X3 adds a different capability: dedicated component layers describing the physical components used for assembly.
What does Gerber X3 add?
Gerber X3 was introduced to extend Gerber data into PCB assembly. It adds component layers for the top and bottom sides of a board, using the familiar Gerber syntax together with component-specific attributes.
Depending on what the PCB design system exports, an X3 component layer can describe information such as:
Placement
The component location, side and rotation on the finished PCB.
Identification
Reference designators and other identifiers associated with placed components.
Geometry
Component outlines, footprints, pin locations and related assembly geometry.
Part information
Component-specific attributes such as manufacturer and manufacturer part number when provided.
This information is valuable to electronics manufacturing services and assembly teams because it keeps component placement data within the same standardized family of files as the fabrication layers.
Gerber X2 and X3 compared
| Capability | Gerber X2 | Gerber X3 |
|---|---|---|
| Primary purpose | PCB fabrication data with standardized design intent. | Extends Gerber into PCB assembly with component data. |
| PCB layer images | Yes: copper, mask, paste, legend, profile and other layers. | Yes. X3 retains the X2 fabrication foundation. |
| Layer identification | Yes, through file attributes. | Yes. |
| Pad and via functions | Yes, through aperture and object attributes. | Yes. |
| Net, component and pin attributes on image objects | Supported when included by the exporter. | Supported as part of the X2 foundation. |
| Dedicated component layers | No. | Yes, for top-side and bottom-side components. |
| Component placement and rotation | Not represented as a complete component layer. | Supported when included by the exporter. |
| Manufacturer part information | Not the focus of X2 fabrication layers. | Can be included through component attributes. |
| Compatibility with basic Gerber rendering | The image remains valid if attributes are ignored. | Uses Gerber syntax; component-aware software is needed to use the assembly meaning. |
How can you recognize X2 or X3 data?
The filename extension alone is not reliable. Files may use extensions such as .gbr, .ger, .pho or layer-specific names regardless of whether attributes are present.
X2 and X3 are identified by their contents. X2 introduced attribute commands such as TF, TA, TO and TD. An X3 dataset includes component layers identified through the appropriate file-function attributes and component-specific data.
A capable viewer can interpret these attributes and present the information in a readable form, avoiding the need to inspect the Gerber source text manually.
Viewing X2 and X3 information with GerbView
GerbView can open and display Gerber X2 and X3 files together with other PCB manufacturing data. It reads supported attributes and makes available information easier to inspect alongside the visible PCB layers.
- Identify layer functions from Gerber attributes.
- Inspect supported file, aperture and object attributes.
- List and highlight available PCB nets.
- Review component reference designators, placement and rotation.
- Inspect component pins, footprints and related metadata when present.
- Control layer visibility, ordering, colors and transparency.
- Measure, print, compare and convert supported PCB data.
The available information depends on the exported files
Opening a file in an X2- or X3-capable viewer cannot recreate metadata that was not exported. The PCB design system must include the relevant attributes and component layers when generating the manufacturing package.
Should you use Gerber X2 or X3?
Use X2 when transferring PCB fabrication data and your design software and manufacturing partner support it. The standardized attributes reduce reliance on filename conventions and make the purpose of layers and image objects clearer.
Use X3 when you also want to transfer component information for assembly and your downstream workflow supports X3 component layers. Because X3 builds on X2, the practical choice is not normally “X2 or X3” as competing formats. It is whether the manufacturing package should contain X2 fabrication data alone or X2 fabrication data together with X3 component data.
Always confirm the required output with your PCB fabricator or assembly provider. Their accepted package structure and validation requirements remain decisive.
Frequently asked questions
What is the main difference between Gerber X2 and X3?
Gerber X2 adds standardized attributes that communicate PCB fabrication intent, including layer functions, pad and via functions, and component-pin-net relationships. Gerber X3 builds on X2 by adding dedicated component layers containing placement and assembly information.
Does Gerber X3 replace Gerber X2?
No. X3 extends the attribute-based Gerber format used by X2. The fabrication layer information remains relevant, while X3 adds component data for assembly workflows.
Does Gerber X2 contain net information?
It can. X2 object attributes can identify the net, component reference and pin associated with graphical objects. The exporting CAD system must include these attributes.
Can a normal Gerber viewer display X2 files?
A viewer that supports the underlying Gerber image commands can normally display the geometry because X2 attributes do not change the image. However, software must understand the attributes to expose the additional design-intent information.
Can GerbView display Gerber X2 and X3 information?
Yes. GerbView supports Gerber X2 file and object attributes and can display available component, pin and net information from compatible Gerber X3 and X2 datasets.
Related information
Technical references
Inspect Gerber X2 and X3 data with GerbView
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