What Is a Gerber File? The Complete Guide for PCB Design & Manufacturing

If you've ever tried to order a custom PCB, you've probably run into one question almost immediately: where do I upload the Gerber files? For first-timers, it can feel like a gatekeeping moment. But once you understand what Gerber files actually are, the whole PCB manufacturing process starts to make a lot more sense.

This guide covers everything — from what a Gerber file is and what's inside it, to how to generate one, verify it, and submit it correctly to your manufacturer.

What Is a Gerber File?

A Gerber file is the industry-standard file format used to communicate a PCB design to a manufacturer. Think of it as the construction blueprint for your board. It tells the fabrication machines exactly where to place copper traces, where to apply solder mask, where to drill holes, and more.

Each Gerber file describes a single layer of the PCB as a 2D vector image. A complete PCB design is typically packaged as a set of Gerber files (one per layer) compressed into a .zip folder. Files use the .gbr or .ger extension.

Gerber File Layers: What's Inside the Package

So what exactly goes into that zip folder? A typical Gerber package contains one file per layer, and each layer serves a specific purpose in the manufacturing process. The table below breaks down the most common layers, what they do, and the file extensions you'll typically see:

Note: The drill file (Excellon format) is technically a separate format, but it's always included as part of your Gerber package submission. Missing it is one of the most common reasons manufacturers reject a file set.

Gerber File Format Versions

Not all Gerber files are created equal. There are three main format versions you'll encounter:

· RS-274D (Standard Gerber) — The original format from the 1980s. It requires a separate aperture file to define shapes, which makes it error-prone and is largely obsolete today.

· RS-274X (Extended Gerber) — The current industry workhorse. Aperture definitions are embedded directly in the file, making it self-contained and far more reliable. Most manufacturers accept this as their default.

· Gerber X2 — The latest standard. Builds on RS-274X by embedding metadata (layer function, polarity, part number, etc.) directly into the file header. It doesn't change the image data, but gives manufacturers much richer context — reducing back-and-forth communication. Increasingly required by modern fab houses.

When in doubt, export RS-274X for maximum compatibility. If your manufacturer supports Gerber X2, it’s usually worth using it for the extra clarity and fewer chances of misinterpretation.

Gerber vs. Other PCB File Formats

Gerber isn't the only game in town. Here's how the three main formats compare:

For most PCB orders, especially fabrication-only jobs, Gerber X2 or RS-274X is usually the safest bet. If you're also sending files for assembly, ODB++ and IPC-2581 tend to work better because they carry more complete manufacturing data.

How to Generate Gerber Files

The exact steps vary by software, but the logic is the same: run a design rule check (DRC) first, then export.

Altium Designer

1. Open your PCB file → File → Fabrication Outputs → Gerber Files

2. Set units, format (RS-274X or X2), and select layers

3. Generate drill files separately via NC Drill Files

4. Output goes to your project's Fab folder

KiCad

1. Open PCB editor → File → Plot

2. Select Gerber format, choose layers, set output folder

3. Click "Generate Drill Files" separately

4. Review output in the built-in Gerber viewer before zipping

Eagle

1. Open board file → CAM Processor

2. Load a standard Gerber job file (e.g., gerb274x.cam)

3. Process all layers and export

Universal tips regardless of software:

· Always run DRC before exporting

· Use millimeters and 4:6 format for precision

· Export drill files in Excellon format alongside your Gerbers

· Double-check that every required layer is included

How to View and Verify Gerber Files

Never send Gerber files straight to a manufacturer without reviewing them first. A misaligned layer or missing drill file can result in a scrapped order.

Recommended free viewers:

· gerbv — Open-source, offline, lightweight. Great for quick checks.

· Altium 365 Viewer — Free online viewer, no account required. Handles most formats.

· KiCad PCB Viewer — Built into KiCad, accurate rendering of your own exports.

What to look for:

· Are all layers present and visible?

· Do copper layers align with solder mask cutouts?

· Are drill holes centered on the correct pads?

· Does the board outline form a closed shape?

· Are units consistent (don't mix mm and inches)?

Pre-Submission Checklist

Before uploading to any manufacturer, run through this list:

• All required layers are exported (copper, mask, silkscreen, outline, drill)

• File naming follows a clear convention (.GTL, .GBL, .GTS, etc.)

• Units are consistent throughout all files

• Gerber files have been visually verified in a viewer

• Drill file is included and in Excellon format

• Format version matches what your manufacturer accepts (RS-274X is safest)

FAQs

1. What files are included in a Gerber package?

Typically: copper layers (top/bottom), solder mask layers, silkscreen layers, board outline, and a drill file. Multi-layer boards add inner copper layers.

2. What's the difference between a Gerber file and a BOM?

A Gerber file defines the physical board — traces, pads, layers. A BOM (Bill of Materials) lists the components that get soldered onto it. Both are needed for assembly orders.

3. Which Gerber format should I send to my manufacturer?

RS-274X is universally accepted. Gerber X2 is preferred by modern fabs. When in doubt, ask your manufacturer directly — most specify it on their upload page.

4. Can Gerber files be edited?

Technically yes, using tools like GerbMerge or Altium's Gerber editor, but it's not recommended unless necessary. It's almost always better to fix issues in your PCB layout and re-export.

Conclusion

Gerber files are the universal language of PCB manufacturing — the bridge between your design and the factory floor. Get them right, verify them before submission, and the rest of the process becomes straightforward. When you're ready to fabricate, PCBgogo makes it easy to upload, quote, and order — all in one place.