A Gerber file is a PCB manufacturing file that describes one two-dimensional board layer. If you send a printed circuit board to a manufacturer, the Gerber package is the set of files that tells the CAM department where copper, solder mask, silkscreen, paste, and other layer images belong. It is the common handoff between PCB design tools and fabrication equipment.
Gerber is an open, de-facto-standard format. The format originated with Gerber Systems Corp., and it is now owned and maintained by Ucamco, which publishes the Gerber specification. That history matters because the word Gerber is sometimes used loosely for any PCB manufacturing ZIP, but the actual format has a defined syntax and a current maintainer.
If you already have files, open them in the Gerber viewer and inspect the rendered layers. To understand the hole files that normally travel with them, read the Gerber versus drill file guide.
Quick answer
A Gerber file is an ASCII vector image file for one PCB layer. It tells a manufacturer the exact 2D shapes for copper, solder mask, silkscreen, paste, outline, or another manufacturing image. Modern Gerbers are usually RS-274X or Gerber X2, and drill holes are normally supplied separately as Excellon drill files.
What a Gerber file describes
Gerber is a vector format, not a screenshot. The file contains commands that define coordinates, apertures, flashes, draws, arcs, and filled regions. A CAM system reads those commands and reconstructs the layer artwork. A copper layer might contain traces, pads, pours, thermal reliefs, and clearances. A solder mask layer describes openings in the mask where copper should remain exposed. A silkscreen layer describes printed markings such as reference designators, polarity marks, and labels.
The format is image based. It says where material or openings should appear on a flat PCB layer. It does not carry the full editable design intent from your CAD project. For example, a Gerber can show a copper trace, but it does not know that the trace came from a routed net with a specific design rule unless additional metadata is present in a richer format or in Gerber X2 attributes.
One file per layer
A typical PCB release has many Gerber files. Top copper is one file. Bottom copper is another. A four-layer board adds inner copper layer files. Top and bottom solder mask, top and bottom silkscreen, paste layers for stencil production, and a board outline or mechanical layer may each be exported separately. These files are usually gathered into a ZIP so the board house receives the complete set together.
Drill data is the important exception. Holes are normally supplied in Excellon drill files, not inside the copper Gerbers. Copper pads can show where holes should be centered, but the drill machine still needs hole coordinates, tool diameters, and plating information. That is why a complete fabrication package normally includes both Gerbers and drill files.
Modern Gerber versions
Modern PCB exports normally use RS-274X, also called Extended Gerber, or Gerber X2. RS-274X made Gerber files self-contained by embedding aperture definitions and format settings in the file. Older RS-274D files depended on a separate external aperture list, which made missing or mismatched apertures a common source of historical CAM problems.
Gerber X2 builds on RS-274X by adding attributes. These attributes can identify layer function, aperture function, component pads, vias, nets, and other useful metadata while remaining compatible with viewers that only render the image. For beginners, the practical point is simple: when your EDA tool offers RS-274X or X2, use the modern output unless your manufacturer gives a specific reason not to.
What Gerber contains and does not contain
| Item | In a Gerber file? | Notes |
|---|---|---|
| 2D layer geometry | Yes | Copper, mask, silk, paste, outline, and drawing images. |
| Apertures, draws, flashes, and regions | Yes | These are the basic image-building elements of the format. |
| Layer function metadata | Sometimes | Gerber X2 can include attributes such as top copper or mask. |
| Drill tool table and hole coordinates | No | Usually supplied as separate Excellon drill files. |
| 3D board model | No | Gerber is a 2D manufacturing image format. |
| BOM or pick-and-place data | No | Assembly data is sent as separate files when needed. |
Why manufacturers still rely on Gerber
Gerber remains widely used because it is simple, precise, open, and supported by nearly every PCB CAM workflow. A manufacturer does not need your editable PCB project to fabricate the board. They need reliable layer images, drill data, stackup instructions, and any special notes. Gerber provides the layer images in a tool-neutral way.
The format also makes visual review practical. You can compare the files you are about to order with the board you expected to export. Because Gerbers are the actual manufacturing output, checking them can reveal missing outlines, mirrored text, old bottom layers, absent paste openings, or drill alignment problems before those mistakes reach the manufacturer.
See it in the viewer
The fastest way to make Gerber files less abstract is to open a real package. Load the ZIP in the Gerber viewer and toggle layers one at a time. Watch how top copper differs from top mask, how silkscreen is only printed legend, and how drill hits align with pads and vias. If you are not sure which extensions mean which layers, continue with the Gerber layer extensions guide.
FAQ
- Is a Gerber file editable?
- A Gerber file can be edited with CAM software, but it is not the same as editing the original PCB design. Treat Gerbers as manufacturing outputs and make design changes in the source EDA project when possible.
- Do all PCB manufacturers accept Gerber files?
- Gerber is the de-facto standard PCB fabrication image format and is accepted very broadly. Always check the manufacturer instructions because they may also ask for drill files, stackup notes, or assembly files.
- Is a Gerber release one file or many files?
- A normal release is many files, usually one Gerber per PCB layer or manufacturing image, plus separate Excellon drill files and any supporting notes or reports.
- Can I open Gerber files without the original CAD software?
- Yes. Gerber files are exchange outputs, so you can open them in an independent Gerber viewer without KiCad, Altium Designer, EAGLE, EasyEDA, or the source project.