Format Odyssey

FILE FORMAT GUIDE

OBJ File (.OBJ): Geometry, MTL Files & Opening

An OBJ file is a line-oriented text format for 3D surface geometry. It can describe vertices, faces, lines and free-form surfaces and may reference a separate MTL material file and texture images.

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Quick facts

Extension
.obj
Format
Wavefront OBJ
Category
3d
MIME type
model/obj
Standard / developer
Wavefront Technologies (origin); IANA registration
Open with
macOS Preview

What is OBJ?

OBJ elements refer to vertices by their position in the file. Common polygonal models use v and f records, but the specification also permits curves and surfaces that not every importer supports. Companion assets must travel with the OBJ when appearance matters.

  • Exchange polygonal surface geometry between 3D applications

How to open OBJ

The cited format review records Preview support, but OBJ importer coverage varies. Preserve all companion files and the original model.

macOS PreviewmacOS desktop application

Keep the OBJ beside its referenced MTL and textures, then open the OBJ in Preview. Inspect whether materials and colors appeared; support for one model does not establish support for every OBJ statement.

Technical details

Signature
No registered magic number
Encoding
Line-oriented plain text; character encoding is not declared by the filename
Container
Not applicable
Compression
Not inherent to the format

Library of Congress Wavefront OBJ description

Things to check

  • Materials and textures can depend on separate MTL and image files.
  • Importers vary in support for free-form curves, surfaces and coloring conventions.

Related formats

  • STereoLithography

    Another surface-geometry exchange format, usually with fewer appearance references.

  • glTF JSON Asset

    A runtime-oriented scene format that can represent materials, scenes and animation beyond common OBJ workflows.

  • 3D Manufacturing Format

    A packaged manufacturing format with explicit units and extensible model resources.

Sources & review

Fact review: 2026-09-19. Unknown fields are not inferred from the file extension.