RS-274X includes many high level commands and controls that let the creator of the Gerber data specify the PCB (photoplot) very precisely. The file contains all critical information.

RS274X is an extension to standard RS-274D (commonly known as Gerber) that includes:

  • Embedded format, unit and data information
  • Embedded apertures
  • Custom aperture definitions
  • Film control statements
  • Multiple layers embedded in a single file
  • Special polygon definitions

The RS-274X specification was originally developed by Gerber Systems.

Determine if your Gerber files are in RS-274X format or RS-274D format.

Open a Gerber file with a text file editor like ( Notepad, Wordpad,… )
If the files are in RS-274X format the aperture definitions will be embedded at the beginning of your file. There will also be a header which shows the coordinate format and other options you have selected when generating the Gerber output.

Example: %FSLAX24Y24*% this means : Format Statement Leading Zeros Suppression, Absolute Coordinates format=2.4.

The syntax is defined in the following image:

RS-274X Format statement


L = leading zeros omitted
T = trailing zeros omitted
D = explicit decimal point ( meaning that no zeros are omitted)

A = absolute coordinate mode
I = incremental coordinate mode

Nn = sequence number, where n is number of digits ( rarely used)

Gn = preparatory function code ( rarely used)

Xa = format of input data ( 5.5 is max)

Yb = format of input data

Zb = format of input data ( Z is rarely, if ever seen)

Dn = draft code

Mn = misc code

Example of embedded aperture list:


The synax is:


AD – aperture description parameter
D{code} d-code to which this aperture is assigned (10-999)
C tells 274X this is a circle macro
R tells 274X this is a rectangle macro
$1 value (inches or mm) of the outside diameter
$2 optional, if present defines the diameter of the hole
$3 optional, if present the $2 and $3 represent the size of
a rectangular hole.

If you see the aperture macros present in your files then you definitely have files in RS-274X format.

A free Gerber & DPF viewer ( GC-Preview) can be downloaded from Graphicode. We have experience with this viewer, so we can help you if needed.