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IGS converter

An .igs file contains IGES CAD data under the abbreviated extension that early file systems, limited to three characters, forced on the format. Nothing but the name differs from .iges: the same punch-card-style text encodes the same curves, surfaces, and drawing entities.

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Drop IGS files here

Batch files can each use a different output. Nothing uploads for local conversions.

Working inputs include camera RAW, browser-local audio/video, PDF, CBZ/CBR comics, office documents, ebooks, markup, 3D models, structured text, images, and archives.

Where IGS comes from

IGES predates long filenames — it launched in 1980 when three-character extensions were the rule, so .igs was for years the more common spelling. Even after the final 5.3 revision of the specification, exporters kept the short form as their default, which is why archives contain vastly more .igs than .iges files.

How IGS works

  • The same five-section, 80-column record structure as .iges, with a letter code in column 73 marking each section.
  • Entity types are identified by standardized numbers — 126 for rational B-spline curves, 128 for NURBS surfaces, 144 for trimmed surfaces.
  • Extension choice has no effect on parsing; renaming between .igs and .iges is lossless by definition.
  • Trimmed-surface models dominate real-world files, and their tolerance mismatches are the usual cause of import gaps.

When to use IGS

  • Reading decades-old supplier geometry that shipped with the short extension
  • Feeding legacy toolpath and inspection systems that filter strictly on .igs
  • Bridging to receiving systems that predate STEP adoption

Strengths and limitations

Strengths

  • Matches .iges fidelity exactly
  • Ubiquitous import support across engineering software
  • The short extension satisfies legacy systems that reject longer names

Limitations

  • Two spellings for one format regularly confuse file filters and format lists
  • Carries all of the specification's age: weak solids, sparse metadata, and frequent healing work after import

Compatibility

CAD import dialogs treat .igs and .iges as one entry, so support spans SolidWorks, CATIA, NX, Rhino, FreeCAD, and effectively everything else in the field. As with its long-named twin, there is no operating-system or browser support, and conversion to STEP or a mesh format is typical for downstream use.

The same Global-section fields as the longer spelling: sender, author, units, and timestamps, and little else.

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