GTS File

What are GTS files and how to open them

Are you having problems opening a GTS file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your GTS files.

What is a GTS file?

A .GTS file is a Gerber Top Solder Mask file.

Used for printed circuit board fabrication, this file holds the top solder mask layer. It describes where to leave openings in the protective mask on the board's top side so solder can reach the copper pads. This layer is produced by PCB layout software when preparing Gerber export using an open standard like RS-274X. It is then used by manufacturing tools and photoplotters to generate masks for solder-resist material.

It is part of a set of Gerber layer files defining each layer of the PCB: copper (top, bottom, inner), solder mask (top, bottom), legend or silkscreen, paste mask, board outline, and drill data. The file is usually generated by tools like Altium Designer under a layer export setting "Top Solder Mask (.GTS)" following naming conventions. Manufacturers use it along with other layers to build the finished board.

It must adhere to the Extended Gerber (RS-274X) specification, which requires headers defining coordinate format, units, zero suppression, and embedded aperture definitions. For a file representing the top solder mask, the "FileFunction" attribute is set to "Soldermask,Top" or similar. The image inside usually has negative polarity so that the mask opens are rendered (exposing copper) against the mask coating. The file is textual, ASCII-based.

Technical note: RS-274X Gerber files consist of data blocks ending with the "" character. Header directives like %FSLAX...% or %MO...% set coordinate format and units, aperture definitions use %ADD...% statements, and the FileFunction attribute appears in a TF statement near the start, e.g. %TF.FileFunction,Soldermask,Top*%.

How to open GTS files

We have identified one GTS opener that is compatible with this specific type of GTS file.

Programs that open Gerber Top Solder Mask files

Last updated: August 6, 2026

Various apps that use files with this extension

These apps are known to open certain types of GTS files. Remember, different programs may use GTS files for different purposes, so you may need to try out a few of them to be able to open your specific file.

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