What is Gerber File in PCB? Gerber File Format, Gerber File Extension

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What Is a Gerber File?

A Gerber file is the standard file format used for PCB (Printed Circuit Board) manufacturing. It contains all the details needed to create a PCB, including copper traces, solder masks, drill holes, and silkscreen markings. Think of it as a blueprint for circuit boards—without it, manufacturers wouldn’t know how to fabricate your design.

This file format was developed by Gerber Systems Corp and has been widely adopted in the electronics industry. When a PCB designer completes a circuit board layout, they export the design as a Gerber file, which is then sent to the manufacturer for fabrication. Some manufacturers will make the PCBs directly according to this file. But in Best Technology, our engineering team will optimize this gerber file, such as trace width, add fiducial marks to smooth production and improve the utilization rate of raw materials. The file after optimization we called Working Gerber File (WG/WF), and it will be sent to customer for final approval.

What is Gerber File in PCB? Gerber File Format, Gerber File Extension

Why Is a Gerber File Important for PCB Manufacturing?

A Gerber file provides a precise digital blueprint of the circuit board design. Without these files, manufacturers would have no clear instructions on how to fabricate the board, leading to potential misinterpretations or errors. Gerber files are not standard image or single document file but rather a collection of files. Each file represents a different layer of the PCB, such as:

Copper layers (for electrical connections)
Solder mask layers (to protect copper traces)
Silkscreen layers (for text and symbols)
Drill data files (for hole placements)

Without Gerber files, a PCB manufacturer wouldn’t have the necessary layer information for PCB manufacturing.

Gerber File Format

Nowadays, Gerber files exist in two primary formats:

1. RS-274D (Older Version)

Requires an aperture file to define shapes and sizes.
Can cause compatibility issues with modern PCB software.
Still used by some manufacturers, but largely replaced by the newer format.

2. RS-274X (Current Version)

Includes aperture definitions within the file, making it easier to process.
Supports polarity settings, layer information, and additional metadata.
Preferred by most PCB manufacturers because of better accuracy and compatibility.

For engineers and designers, if you’re generating Gerber files for PCB production, it’s best to use the RS-274X gerber file format to avoid errors during fabrication.

Gerber File Extension

Generally, we see a lot of extensions in a gerber file. Each gerber file extension means one layer, indicating which layer it represents. Here are some common extensions and their meanings when I faced during daily workings:

.GTL – Top Copper Layer
.GBL – Bottom Copper Layer
.GML or .G1, G2, etc. – Inner Copper Layers (for multilayer PCBs)
.GTS – Top Solder Mask
.GBS – Bottom Solder Mask
.GTO – Top Silkscreen (component labels, markings, logos)
.GBO – Bottom Silkscreen
.GTP – Top Solder Paste (for stencil printing)
.GBP – Bottom Solder Paste
.DRL – Drill Data (defines hole sizes and locations)
.TXT or .EXCELLON – Drill Tool List (used with .DRL file)
.GM1 – Mechanical Layer (board outline, cutouts, milling)
.GKO – Keep-Out Layer (defines restricted areas for components)
.GM3 – Additional Mechanical Layer (if multiple mechanical layers exist)
.FAB – Fabrication Layer (contains PCB fabrication details)
.DXX – Drill Drawing (used to document drill hole placements, rarely to use)
.NC – NC Drill File (numerical control drilling instructions)

How do I Open a Gerber File?

Since Gerber files are not text or image files, you need special software to open and view them. Many PCB design tools include built-in Gerber viewers.

Popular Gerber Viewers:

Altium Designer – Used by professional PCB designers.
KiCad – Free and open-source.
Gerbv – A lightweight Gerber viewer.
CAM350 – A versatile gerber viewer
Online Gerber Viewers – Available for quick viewing without software installation.

Herein, Best Team will teach you how to open the gerber file by CAM350 step by step:

1. Open the Gerber Files

Launch CAM350 and open the project containing the Gerber files.

2. Import Gerber Files

Click File > Import > Gerber Data and select all the relevant Gerber files for your PCB.

3. Identify the Different Layers

Once the Gerber files are loaded, you’ll see multiple layers in different colors. Each file corresponds to a specific PCB layer, just I mentioned as above. You can import the layer what you want import and import all layers.

4. Analyze the Design Features

Use zoom and pan tools to inspect individual traces and pads.
Toggle layers on or off in the Layer Panel to isolate specific details.
Measure trace widths, pad sizes, and spacing using measurement tools.

How to Convert Gerber to PDF?

Converting Gerber files to PDF is useful for documentation, design review, and sharing with clients or team members who do not have Gerber viewing software. Here are detailed steps to convert gerber to PDF using CAM350:

Import File > Click File > Print or File > Export > PDF.
In the print settings, select PDF as the output format.
Choose whether you want to print single layers or the entire PCB design.
Click Save, and CAM350 will generate a high-resolution PDF file of your Gerber layout.

Setup

Set the parameters before printing, select these points: fit to page > output all data in black (optional) > separate sheets (optional)

2. Verify the PDF Output

Open the PDF file to ensure all details are visible and clear.
If necessary, go back to CAM350, adjust settings, and export again.

Below is the file printed into PDF.

How Do I Download Gerber Files?

To download Gerber files, follow these steps:

In your PCB design software, select the Export Gerber > Gerber Data > Set your file name, layers name, export path > OK button

Here is all the sharing from Best Technology today if you want to know more about gerber files, welcome to contact us, our team are always online to serve you!