Guide

Gerber Format: The PCB Manufacturing Standard for Circuit Board Data

PC By Pablo Cirre • Updated May 7, 2026

What Is the Gerber Format?

Gerber is the de facto standard file format for describing printed circuit board (PCB) artwork — the copper traces, solder mask openings, silkscreen legends, and board outlines that PCB manufacturers use to fabricate circuit boards. Originally developed by Gerber Scientific Instruments in the 1960s for vector photoplotter machines, Gerber has evolved through several versions into the modern RS-274X (Extended Gerber) standard, now maintained and freely published by Ucamco (who acquired the Gerber technology in 2012).

When you order a PCB from any fabricator — JLCPCB, PCBWay, OSH Park, Advanced Circuits, or any professional fab — you submit a set of Gerber files. Every PCB CAD tool can export Gerber; every fabrication house accepts it. It is the PostScript of the electronics manufacturing world.

The Gerber File Set

A complete PCB is described by a set of Gerber files, each representing one layer:

Layer	Typical Extension	Description
Front copper	`.GTL` (Top Layer)	Top-side copper traces and pads
Back copper	`.GBL` (Bottom Layer)	Bottom-side copper
Inner layers	`.G1`, `.G2`, …	Internal copper layers for multilayer boards
Front solder mask	`.GTS` (Top Solder)	Openings in the green lacquer — exposes pads
Back solder mask	`.GBS` (Bottom Solder)	Bottom-side mask openings
Front silkscreen	`.GTO` (Top Overlay)	Component labels and reference designators
Back silkscreen	`.GBO` (Bottom Overlay)	Bottom-side text
Board outline	`.GKO` or `.GM1`	Edge cuts — defines the PCB shape
Drill file	`.DRL` or `.XLN`	Excellon-format drill coordinates and sizes
Paste mask	`.GTP`, `.GBP`	Stencil openings for solder paste application

KiCad (the dominant open-source PCB EDA tool) exports this exact structure by default. Altium Designer uses a similar naming convention with .GTL, .GBL, .GTS, etc.

RS-274X Format Structure

A Gerber file is a plain ASCII text file. The format is command-based:

%FSLAX46Y46*%         ; Format Specification: 4 integer, 6 decimal digits, absolute coords
%MOMM*%               ; Units: Millimeters
%LPD*%                ; Layer Polarity: Dark (default)

; Aperture definitions
%ADD10C,0.200000*%    ; Aperture #10: Circle, diameter 0.200000 mm
%ADD11R,1.600000X0.800000*%  ; Aperture #11: Rectangle, 1.6mm × 0.8mm
%ADD12O,1.000000X0.600000*%  ; Aperture #12: Oblong (rounded rect), 1.0mm × 0.6mm
%ADD13P,0.500000X6*%  ; Aperture #13: Regular polygon, 0.5mm diameter, 6 sides

; Commands
D10*                  ; Select aperture #10 (0.2mm circle)
X150000Y200000D02*    ; Move to (1.500000, 2.000000) mm — no draw
X300000Y200000D01*    ; Linear draw to (3.000000, 2.000000) mm
X450000Y200000D03*    ; Flash aperture at (4.500000, 2.000000) — creates a pad

D11*                  ; Switch to rectangle aperture
X250000Y150000D03*    ; Flash SMD pad

G01*                  ; Linear interpolation mode (default)
G02*                  ; Clockwise arc interpolation
G03*                  ; Counter-clockwise arc interpolation

M02*                  ; End of file

Coordinates are encoded as integers with implicit decimal points — X150000 with format X46 means 1.500000 mm (4 integer digits + 6 decimal digits).

Apertures in Detail

Apertures define the shapes used to draw traces and flash pads:

Aperture Type	Code	Description	Use
Circle	`C`	Diameter parameter	Round traces, round pads
Rectangle	`R`	Width × Height	SMD component pads
Oblong	`O`	Width × Height	Elongated pads
Polygon	`P`	Diameter, vertices, rotation	Hex/octagon pads
Macro	`%AMNAME*...%`	Arbitrary complex shape	Custom pad shapes

Macros can define complex shapes using primitives like circles, lines, and rectangles combined with arithmetic expressions:

%AMTHERMAL*
1,1,0.6,0,0,0*          ; solid circle, diameter 0.6mm
1,0,0.4,0,0,0*          ; clear circle, diameter 0.4mm
20,1,0.15,-0.3,0,0.3,0,0*  ; line across horizontal
20,1,0.15,0,-0.3,0,0.3,0*  ; line across vertical
%

This macro defines a thermal relief aperture — a pad with spokes connecting it to a copper pour, reducing heat sinking during soldering.

The Excellon Drill File

The drill file is a companion to the Gerber set, typically in Excellon format (not technically Gerber, but always distributed alongside):

%
FMAT,2
METRIC,TZ
T1C0.300        ; Tool #1: 0.3mm diameter
T2C0.600        ; Tool #2: 0.6mm diameter
T3C1.016        ; Tool #3: 1.016mm diameter (standard through-hole pin)
%
G90             ; Absolute coordinates
G05             ; Drill mode
T1              ; Select 0.3mm drill
X0.45Y0.35      ; Drill at (0.45, 0.35) mm
X1.25Y0.35      ; Drill at (1.25, 0.35) mm
T2              ; Select 0.6mm drill
X2.50Y1.10      ; Drill at (2.50, 1.10) mm
T3              ; Select 1.016mm through-hole drill
X0.85Y2.10
M30             ; End of file

Modern fabricators accept drill files in Excellon 2 format, which adds units headers and tolerances. KiCad generates .drl files automatically alongside the Gerber export.

Gerber X2: Structured Metadata

Gerber X2 (released 2014, standardized as IPC-2581 alternative) adds structured metadata attributes embedded as comment lines:

%TF.FileFunction,Copper,L1,Top*%      ; This file = copper, Layer 1, Top
%TF.FilePolarity,Positive*%           ; Dark apertures = copper
%TF.SameCoordinates,Original*%        ; All files share same coordinate origin
%TF.CreationDate,2024-03-15T14:30:00*%
%TF.GenerationSoftware,Kicad,Pcbnew,8.0.1*%
%TF.ProjectId,MyProject,{uuid},1.0*%

%TA.AperFunction,SMDPad,CopperDef*%   ; Next aperture defines an SMD pad
%ADD10C,0.2*%

Gerber X2 attributes allow automated CAM software to understand which layer is which without relying on file naming conventions — critical when file names get scrambled by email clients or zip utilities.

Exporting Gerbers from KiCad

KiCad's Gerber export workflow:

Open PCB editor → File → Fabrication Outputs → Gerbers
Select output folder and layers to export
Enable Use Protel filename extensions (GTL, GBL, etc.) for maximum fab compatibility
Enable Generate drill files → select Excellon format
Click Plot and Generate Drill Files
Zip the folder and upload to your PCB fab

# Automated KiCad Gerber export via scripting (KiCad 7+)
import pcbnew

board = pcbnew.LoadBoard("myboard.kicad_pcb")
pctl = pcbnew.PLOT_CONTROLLER(board)

popt = pctl.GetPlotOptions()
popt.SetOutputDirectory("./gerbers/")
popt.SetPlotFrameRef(False)
popt.SetUseGerberX2format(True)
popt.SetIncludeGerberNetlistInfo(True)

# Plot each layer
for layer_id, suffix in [(pcbnew.F_Cu, "GTL"), (pcbnew.B_Cu, "GBL"),
                          (pcbnew.F_Mask, "GTS"), (pcbnew.B_Mask, "GBS"),
                          (pcbnew.F_SilkS, "GTO"), (pcbnew.Edge_Cuts, "GKO")]:
    pctl.SetLayer(layer_id)
    pctl.OpenPlotfile(suffix, pcbnew.PLOT_FORMAT_GERBER, suffix)
    pctl.PlotLayer()
    pctl.ClosePlot()

Viewing and Validating Gerber Files

Before submitting to a fab, always inspect your Gerbers with a viewer:

KiCad GerbView (free, included with KiCad) — open multiple layers, check alignment
Gerbv (free, open-source, Linux/Windows/macOS)
ViewMate (Pentalogix, free tier) — industry standard on Windows
GerberHub.io — web-based, drag-and-drop, instant preview
EasyEDA Gerber Viewer — web-based

Check for: missing layers, misaligned drill holes on pads, unintentional copper shorts, silkscreen overlapping solder mask openings.

Reading Gerber Files with Python

pygerber provides full RS-274X parsing:

from pygerber.gerberx3.api.v2 import GerberFile

# Parse and render a Gerber file to PNG
file = GerberFile.from_file("board_top_copper.gtl")
image = file.parse().render_with_pillow()
image.save_as("top_copper_preview.png")

Related conversions

Frequent conversions across the catalogue:

Frequently Asked Questions

A Gerber file (RS-274X format) is an ASCII text file describing one layer of a printed circuit board — where copper traces go, where pads are, which areas are masked, what text appears on the silkscreen. A complete PCB requires a set of Gerber files (one per layer) plus an Excellon drill file. You submit this zip to a PCB fabricator like JLCPCB or PCBWay, and they use it to drive the photoplotter, solder mask exposure machine, and drill press that manufacture your board.

A Gerber arquivo (RS-274X formato) is an ASCII text arquivo describing one layer of a printed circuit board — where copper traces go, where pads are, which areas are masked, what text appears no silkscreen. A complete PCB requires a set of Gerber arquivos (one per layer) plus an Excellon drill file. You submit this zip para um PCB fabricator like JLCPCB ou PCBWay, e they usar it to drive the photoplotter, solder mask exposure machine, e drill press that manufacture your board.

A Gerber Datei (RS-274X Format) is an ASCII text Datei describing one layer eines printed circuit board — where copper traces go, where pads are, which areas are masked, what text appears auf dem silkscreen. A complete PCB requires a set von Gerber Dateien (one per layer) plus an Excellon drill file. You submit this zip zu einem PCB fabricator like JLCPCB oder PCBWay, und they verwenden it to drive the photoplotter, solder mask exposure machine, und drill press that manufacture your board.

A Gerber archivo (RS-274X formato) is an ASCII text archivo describing one layer de un printed circuit board — where copper traces go, where pads are, which areas are masked, what text appears en el silkscreen. A complete PCB requires a set de Gerber archivos (one per layer) plus an Excellon drill file. You submit this zip a un PCB fabricator like JLCPCB o PCBWay, y they usar it to drive the photoplotter, solder mask exposure machine, y drill press that manufacture your board.

On KaijuConverter every file is processed inside an isolated container, encrypted in transit (TLS 1.3) and at rest, and automatically deleted after 60 minutes with multi-pass overwrite. We never train on, share, or analyze user content. For maximum privacy on extremely sensitive material, prefer offline tools (ImageMagick, FFmpeg, LibreOffice) that you control end-to-end.

Original Gerber (RS-274X) describes board geometry only — it has no built-in way to say "this file is the front copper layer." Gerber X2 (2014) adds structured metadata attributes (TF.FileFunction, TF.FilePolarity, TA.AperFunction) as header comment lines. These tell automated CAM software which layer is which without relying on file naming conventions. Most modern PCB EDA tools (KiCad 6+, Altium) export Gerber X2 by default. Always enable X2 export when your fab supports it — it prevents layer assignment errors.

O Gerber original (RS-274X) descreve apenas a geometria da placa — não tem forma padronizada de indicar, por exemplo, "este arquivo é a camada de cobre superior". O Gerber X2 (2014) adiciona atributos de metadados estruturados (TF.FileFunction, TF.Polarity, TA.AperFunction…) que permitem que CAMs e fabricantes identifiquem camadas, polaridades e funções de aberturas automaticamente, sem trabalho manual de mapeamento.

Das ursprüngliche Gerber (RS-274X) beschreibt nur die Platinengeometrie — es gibt keinen standardisierten Weg, um etwa anzugeben "diese Datei ist die obere Kupferlage". Gerber X2 (2014) fügt strukturierte Metadaten-Attribute hinzu (TF.FileFunction, TF.Polarity, TA.AperFunction…), mit denen CAM-Tools und Hersteller Lagen, Polaritäten und Aperturen-Funktionen automatisch erkennen — ohne manuelle Zuordnung.

El Gerber original (RS-274X) describe únicamente la geometría de la placa — no tiene forma estándar de indicar, por ejemplo, "este archivo es la capa de cobre superior". Gerber X2 (2014) añade atributos de metadatos estructurados (TF.FileFunction, TF.Polarity, TA.AperFunction…) que permiten a los CAMs y fabricantes identificar capas, polaridades y funciones de aperturas automáticamente, sin trabajo manual de mapping.

For 95% of use cases, yes — server-side ImageMagick, FFmpeg and LibreOffice produce identical output to the same tools on your laptop. Desktop software wins for: extremely large files (multi-GB), batch jobs of thousands of files, scripted pipelines, or content too sensitive to upload. KaijuConverter caps at 25 MB per file on the free tier (up to 2 GB on paid plans).

The Excellon drill file specifies where to drill holes — coordinates and diameters for vias, through-hole component pins, and mounting holes. It uses a different format than Gerber (originally developed for CNC drill machines by Excellon Automation in the 1970s). They are separate because drilling and photolithography are physically separate manufacturing steps using different machines. Always include the drill file in your Gerber zip — submitting Gerbers without drill data is one of the most common beginner mistakes when ordering PCBs.

The Excellon drill arquivo specifies where to drill holes — coordinates e diameters para vias, through-hole component pins, e mounting holes. It uses a different formato than Gerber (originally developed para CNC drill machines by Excellon Automation no 1970s). They are separate because drilling e photolithography are physically separate manufacturing steps usando different machines. Always include the drill arquivo in your Gerber zip — submitting Gerbers sem drill data is one of the most common beginner mistakes when ordering PCBs.

The Excellon drill Datei specifies where to drill holes — coordinates und diameters für vias, through-hole component pins, und mounting holes. It uses a different Format than Gerber (originally developed für CNC drill machines by Excellon Automation im 1970s). They are separate because drilling und photolithography are physically separate manufacturing steps using different machines. Always include the drill Datei in your Gerber zip — submitting Gerbers ohne drill data is one des most common beginner mistakes when ordering PCBs.

The Excellon drill archivo specifies where to drill holes — coordinates y diameters para vias, through-hole component pins, y mounting holes. It uses a different formato than Gerber (originally developed para CNC drill machines by Excellon Automation en el 1970s). They are separate because drilling y photolithography are physically separate manufacturing steps using different machines. Always include the drill archivo in your Gerber zip — submitting Gerbers sin drill data is one del most common beginner mistakes when ordering PCBs.

Most format conversions are lossy by design — JPG, MP3, MP4, WebP all discard perceptual data to save bytes. Going through a lossy intermediate compounds the loss. To minimize visible/audible drift: convert from the original master, choose a higher quality setting, and avoid converting back and forth between lossy formats.

Gerber files are plain ASCII text — you can open them in any text editor. However, the coordinate system is not human-friendly. For viewing, use KiCad GerbView, Gerbv, or the online GerberHub.io viewer. For editing, it is almost always better to go back to the PCB design source (KiCad, Altium, Eagle) and re-export — editing Gerber directly risks introducing inconsistencies between layers. For Python scripting, the pygerber library provides full RS-274X parsing and rendering.

Gerber arquivos são plain ASCII text — Você pode abrir them in any text editor. Porém, the coordinate system is not human-friendly. para viewing, usar KiCad GerbView, Gerbv, ou the online GerberHub.io viewer. para editing, it is almost always better to go back para o PCB design source (KiCad, Altium, Eagle) e re-export — editando Gerber directly risks introducing inconsistencies between layers. para Python scripting, the pygerber library fornece full RS-274X parsing e rendering.

Gerber Dateien are plain ASCII text — Sie können öffnen them in any text editor. Jedoch, the coordinate system is not human-friendly. für viewing, verwenden KiCad GerbView, Gerbv, oder the online GerberHub.io viewer. für editing, it is almost always better to go back zum PCB design source (KiCad, Altium, Eagle) und re-export — editing Gerber directly risks introducing inconsistencies between layers. für Python scripting, the pygerber library bietet full RS-274X parsing und rendering.

Gerber archivos are plain ASCII text — Puedes abrir them in any text editor. Sin embargo, the coordinate system is not human-friendly. para viewing, usar KiCad GerbView, Gerbv, o the online GerberHub.io viewer. para editing, it is almost always better to go back al PCB design source (KiCad, Altium, Eagle) y re-export — editing Gerber directly risks introducing inconsistencies between layers. para Python scripting, the pygerber library proporciona full RS-274X parsing y rendering.

Yes — KaijuConverter accepts multiple files in a single drop and returns a ZIP. For very large batches (thousands of files) consider command-line tools or our API: <code>find . -name "*.heic" -exec magick {} {.}.jpg \;</code> or similar one-liners scale to millions of files when run locally.