How to Open Gerber Files — Complete Beginner's Guide

What Is a Gerber File?

A Gerber file is the universal standard for communicating PCB manufacturing data between designers and fabrication houses. When you design a PCB in KiCad, Eagle, Altium, or any other EDA tool, you export Gerber files to send to your manufacturer. Each Gerber file describes one layer of your board — the top copper, bottom copper, solder mask, silkscreen, and board outline are all separate files. Drill hole positions are stored in a companion Excellon drill file. Together, these files contain everything a factory needs to fabricate your bare PCB.

Understanding the Gerber RS-274X Format

The RS-274X extended Gerber format is maintained by Ucamco and has been the PCB industry standard since the 1980s. Here is what you need to know about the format structure:

• RS-274X — The main format for copper, mask, and silk layers. Uses D-codes (D01 draw, D02 move, D03 flash) with aperture definitions for trace widths and pad shapes. Regions (G36/G37) define copper fills.
• Excellon — A separate file format for drill holes. Contains tool definitions (diameter) and X/Y coordinates for each hole. Your manufacturer uses this to drill vias and mounting holes.
• Layer files — Each PCB layer is a separate file. Common naming: .gtl (top copper), .gbl (bottom copper), .gts (top mask), .gbs (bottom mask), .gto (top silk), .gbo (bottom silk).
• File extensions — Extensions vary by EDA tool. KiCad uses .gbr, Eagle uses .cmp/.sol, Altium uses .GTL/.GBL. MakerSuite 3D auto-detects all common naming patterns.

Step-by-Step: How to Open Gerber Files Online

Follow these steps to view your Gerber files in a free online viewer with 3D rendering:

1. Export Gerber files from your PCB design tool (KiCad: File > Plot, Eagle: CAM Processor, Altium: File > Fabrication Outputs)
2. Collect all generated files into a single ZIP — include copper layers, mask, silk, outline, and drill (.drl) files
3. Open pcbviewer.app and drag your ZIP file onto the drop zone
4. The Layer Mapping dialog appears — MakerSuite 3D auto-detects most layers, but you can manually reassign any unrecognized files
5. Click Apply and your board renders in full 3D with copper traces, vias, and board outline
6. Optionally include a Pick & Place file (.pos) in the ZIP to see 3D component models placed on the board

Gerber Layer Types Explained

Understanding what each layer file represents helps you verify your Gerber output before sending it to manufacturing:

• Copper layers — Define the electrical traces, pads, and copper fills. Top (.gtl) and bottom (.gbl) for 2-layer boards; inner layers for 4+ layer stackups.
• Solder mask — Defines where the green (or other color) protective coating has openings for soldering. Top mask (.gts) and bottom mask (.gbs).
• Silkscreen — Contains component reference designators (R1, C3, U1), polarity marks, and assembly instructions printed on the board surface.
• Board outline — Defines the physical shape and dimensions of the PCB. Sometimes called Edge.Cuts or mechanical layer. Critical for correct board shape.
• Drill files — Excellon format specifying hole positions and diameters for vias, through-hole components, and mounting holes.

How to Check Gerber Files Before Manufacturing

Sending incorrect Gerber files to a manufacturer wastes time and money. Use a Gerber viewer like MakerSuite 3D to verify these critical items before placing your order:

1. Board outline matches your intended dimensions — measure using the M key tool
2. All copper layers are present and traces are correctly routed — use layer toggle to inspect each layer
3. Drill holes are positioned correctly — check via alignments and mounting hole locations in 3D view
4. Solder mask openings expose the correct pads — toggle the mask layer on/off
5. Silkscreen text is readable and correctly positioned — verify reference designators are not overlapping pads

Gerber File Viewer Options

Several tools can open Gerber files, each with different strengths:

• MakerSuite 3D — Free, online, 3D rendering with automatic net analysis, BOM support, and 5-format compatibility. Best for quick 3D inspection and BOM checking.
• GerbLook — Free online 2D Gerber viewer. Fast and simple but limited to 2D and Gerber-only with no BOM or 3D support.
• ViewMate — Free Windows desktop application by Pentalogix. Good 2D rendering but requires installation and only runs on Windows.
• KiCad GerbView — GerbView built into KiCad. Requires KiCad installation. Solid 2D viewer but no 3D rendering for Gerber files.

Tips for Better Gerber Files

• Always include an Edge.Cuts / board outline file — without it, the viewer cannot determine your board shape
• ZIP all files together for one-click upload instead of dragging individual files
• Include a Pick & Place (.pos) file if you want to see 3D component placement on your Gerber board
• Name your files using standard extensions (.gtl, .gbl, .gts, .gbs) for reliable auto-detection