PCB design glossary
Gerber
AKA: RS-274X, gerber files
The de-facto file format used to send PCB layer artwork to a fab house.
Gerber (RS-274X) files describe each layer of a PCB — copper, soldermask, silkscreen, drill data — as 2D vector artwork. A typical PCB job is a ZIP of multiple Gerber files plus an Excellon drill file.
Almost every PCB fab in the world accepts Gerbers. EDA tools like PCBEditor, KiCad, EasyEDA, and Altium all export to it. You can preview Gerbers in a viewer (such as PCBEditor's free Gerber viewer) before sending them off to fabrication.
What is in a Gerber set
A PCB order is usually a ZIP file with one Gerber file per layer plus a drill file. Names vary by tool, but a typical 2-layer set looks like this:
- Top and bottom copper (for example .GTL and .GBL).
- Top and bottom soldermask (.GTS, .GBS) and silkscreen (.GTO, .GBO).
- Top and bottom paste (.GTP, .GBP), used to make the stencil for assembly.
- Board outline (.GKO or .GM1): the shape the fab cuts out.
- Excellon drill file(s) for plated and non-plated holes.
- Inner copper layers on 4-layer and larger boards (.G1, .G2 and so on).
RS-274X and Gerber X2
RS-274X (extended Gerber) is the format every fab accepts. Gerber X2 adds attributes that say what each file is and what each pad is for, which reduces the chance of a fab misreading a layer. Most modern tools can write both; X2 is the better choice where the fab supports it.
Check before you order
- Open the files in a Gerber viewer and look at every layer, not just the copper.
- Confirm the board outline is closed and on the right layer.
- Check that drill holes line up with pads and vias.
- Make sure the layer count matches what you order.
- Look for silkscreen over pads, which the fab will usually clip.
Work it out with a free tool
Look inside a Gerber set before you send it
Drop the fab's ZIP into the Gerber viewer and check copper, mask, silkscreen and outline layer by layer in the browser. No account needed.
Open the Gerber viewer