What Is an IGS File?

How to open, edit, and convert IGS files

Screenshot of IGS files in Windows 10 that open with ABViewer


A file with the IGS file extension is most likely an IGES Drawing file used by CAD programs for saving vector image data in an ASCII text format.

IGES files are based on the Initial Graphics Exchange Specification (IGES) and used to be a widely used standard for transferring 3D models between different CAD applications. However, lots of programs also rely on the STEP 3D CAD format (.STP files) for the same purpose.

Some files that end in .IGS might instead be Indigo Renderer Scene files used by either Indigo's Renderer or RT program. These IGS files, after having been exported from a 3D modeling program like Blender, Maya, Revit, etc., are then imported into the Indigo software to generate a photorealistic picture.

IGS is also an acronym for technology terms that are unrelated to these file formats, like interactive graphics subsystem, integrated gateway server, IBM Global Services, and integrated gaming system.

How to Open an IGS File

You can open an IGS file in Windows with:

A variety of other IGS file viewer programs include:

You might need an IGS plugin with some of those programs before you're able to import the file. For example, if you're opening the IGS file in SketchUp, try installing the SimLab IGES Importer.

FreeCAD is a free IGS opener for Mac and Linux. The TurboCAD Pro and Vectorworks programs linked above can also open an IGS file on macOS.

There are also online IGS viewers that let you upload your file to view it online. Autodesk Viewer, ShareCAD, and 3D Viewer Online are a few examples. Since these services are run through a web browser, it means you can use them to open the IGS file on Mac, Windows, or any other system, including mobile devices.

To open an IGS file in some programs might only be possible after it's been converted into a different file format that the program can read/import. See the IGS converters below for more information.

You can also open an IGS file with any text editor on any operating system, but it's only useful if you want to see all the numbers and letters that describe the file. Notepad++, for example, can view the text within an IGS file, but remember that doing this doesn't actually let you use the IGES Drawing file in the normal way.

If the IGS file you have is in the Indigo Renderer Scene file format, you can open it on a Windows, Mac, or Linux computer with Indigo Renderer or Indigo RT.

How to Convert an IGS File

Most of the IGS openers from above can probably convert an IGS file to a new file format. eDrawings Viewer, for example, can export your IGS file to EPRT, ZIP, EXE, HTM, and a number of image file formats like BMP, JPG, GIF, and PNG.

CAD Exchanger is an IGS converter for macOS, Linux, and Windows that supports a huge variety of export formats. It lets you convert IGS to STP/STEP, STL, OBJ, X_T, X_B, 3DM, JT, WRL, X3D, SAT, XML, BREP, and a few different image file formats.

To open your IGS file in Revit and similar applications might first require that it exists in the DWG format. You can convert IGS to DWG with AutoCAD and some other Autodesk programs, like Inventor, Maya, Fusion 360, and Inventor.

An IGS to DXF conversion can be performed with those Autodesk software applications too.

makexyz.com has a free online IGS to STL converter that you can use to save your IGES Drawing file to the Stereolithography file format.

Try using the File menu in Indigo Renderer if you need to convert that kind of IGS file to a new file format. There's most likely an Export or Save as option there.

Is Your File Still Not Opening?

If your file doesn't open with the programs mentioned above, or will not save when you try to convert it with an IGS converter, try double-checking the file extension. Make sure the suffix reads ".IGS" and not just something that's spelled similarly.

For example, an IGX file could easily be confused with an IGS file even though IGX files are in a totally different file format—the iGrafx Document format, and thus require an iGrafx program to open it.

The same could be said for many other file extensions like IGR, IGC, IGT, IGP, IGN, and IGMA.

The basic idea here is to make sure that you're researching programs that can open the file you actually have. If you have an IGT file and not an IGS file, for example, then look for IGT file openers, converters, etc.

If you do, in fact, have an IGS file that doesn't open with any of the programs from above, run it through a text editor to see if you can find any text within the file that gives away its file format or the program that was used to build it.

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