A Gerber file is a PCB manufacturing layer image. It describes copper, solder mask, silkscreen, paste, outline, or another two-dimensional board layer. You do not need the original CAD program to open a Gerber file. You need a Gerber viewer that can interpret the layer files and, ideally, load the Excellon drill files that go with them.
Most PCB releases arrive as a ZIP archive rather than a single file. Inside the ZIP are several Gerbers plus drill files and sometimes a readme, job file, or reports. A single .gbr file can be valid, but it is usually only one layer. To understand the board, open the complete ZIP or all loose files together.
The simplest method is this online Gerber viewer. Drag in the ZIP or select the files, then inspect the rendered board without installing KiCad, Altium Designer, EAGLE, EasyEDA, or any other design tool. If you are checking a manufacturing handoff, pair the view with the Gerber versus drill file guide so you know why the drill overlay matters.
Quick answer
Open Gerber files by loading the full ZIP, or all loose layer and drill files together, in a Gerber viewer. This online viewer is the fastest no-install option; gerbv and KiCad GerbView are common free desktop options.
Open Gerbers in the online viewer
- Open the Gerber viewer in your browser.
- Drag the manufacturer ZIP, EDA export ZIP, or selected loose files into the viewer. If you have a ZIP, use it directly so related layers stay together.
- Wait for the files to parse and render. The viewer should identify common copper, mask, silkscreen, outline, and drill layers from file names and Gerber data.
- Turn layers on and off to inspect specific features. Check top copper and bottom copper separately, then overlay drill holes with copper pads and vias.
- Look for the board outline. It may be named as an edge, dimension, mechanical, keepout,
.gko, or.gm1layer depending on the exporting tool. - If you need a visual copy, use the viewer's PNG or SVG export. Those are documentation images, not replacements for the original manufacturing files.
This workflow is useful when someone sends you files from an unfamiliar EDA tool. You do not need to know whether the board was designed in KiCad, Altium Designer, EasyEDA, EAGLE, OrCAD, or another package just to inspect the release outputs. Gerber is the exchange format at this stage.
Free desktop viewers
gerbv is a widely used open-source Gerber viewer. It is a good choice for local inspection, repeatable desktop workflows, and users who prefer not to open design files in a browser. It can load Gerber and Excellon files, show layer stacks, change colors, and export visual formats in supported builds.
KiCad GerbView is another common free option. You do not need to design the board in KiCad to use GerbView as a viewer. It can open Gerber layers and drill files generated by other tools, making it useful when you want a desktop application from a maintained EDA suite.
PCB manufacturers often provide upload viewers too. These are helpful because they show how that manufacturer's CAM intake interprets the package. The tradeoff is that the viewer may be tied to an order flow and may not be as convenient for early design review or confidential third-party checks.
Common Gerber and drill extensions
| Extension | Layer | What it shows |
|---|---|---|
| .gbr / .ger | Generic Gerber | Any PCB image layer when the filename carries the meaning. |
| .gtl | Top copper | Top-side traces, pours, pads, and copper features. |
| .gbl | Bottom copper | Bottom-side traces, pours, pads, and copper features. |
| .gts / .gbs | Top / bottom solder mask | Openings in the solder mask where copper is exposed. |
| .gto / .gbo | Top / bottom silkscreen | Printed legend text, outlines, polarity marks, and labels. |
| .drl / .xln | Excellon drill | Hole coordinates, tool diameters, and sometimes slot data. |
| .gko / .gm1 | Outline or mechanical | Board profile, cutouts, dimensions, or mechanical references. |
Loose files versus ZIP archives
If you receive a ZIP, keep it intact for the first inspection. A ZIP reduces the chance of dropping a drill file, outline layer, or bottom mask file when moving data between systems. It also preserves any support files the exporter included, such as Gerber job files or drill reports.
Loose files are still fine when you know they belong together. Select all related files at once so the viewer can overlay them. Avoid opening only a top copper file and assuming the board is complete. A manufacturable PCB package normally needs copper, solder mask, outline, and drill data, and may also include silkscreen, paste, and assembly information.
If the filenames are confusing, use the rendered view rather than the extension alone. Some CAD tools use generic .gbr names with layer names in the base filename. Others use Protel-style extensions such as .gtl and .gbl. A viewer helps you see whether a file is actually copper, mask, silk, or outline.
When to regenerate instead of just opening
Viewing is enough for inspection, documentation, and confirming that files were received. It is not a substitute for a correct export. If the drill holes do not line up, a board outline is missing, bottom layers are absent, or old files are mixed with new files, regenerate the package from the source PCB tool. The KiCad export guide and EasyEDA export guide show two examples of creating a clean release package.
FAQ
- What opens a .gbr file?
- A Gerber viewer opens .gbr files. You can use this online viewer, gerbv, KiCad GerbView, or a PCB manufacturer viewer depending on whether you want browser-based or desktop inspection.
- Do I need KiCad, Altium, or the original EDA tool to view Gerbers?
- No. Gerber files are manufacturing outputs, so they can be opened by independent Gerber viewers even when you do not have the original PCB design project or EDA license.
- Is it safe to upload Gerbers to this viewer?
- The viewer is designed to process files in the browser for visual inspection rather than requiring the original CAD tool. For highly confidential projects, follow your organization’s data-handling rules before using any web tool.
- What if I only have some Gerber layers?
- You can still open the available files, but the view may be incomplete. Missing outline, drill, mask, or copper layers can prevent a reliable manufacturing review.