What Is an OBJ File (and How to Open One)

What an OBJ file is, why it usually comes with an MTL file, what it's good for, and how to open and inspect one in your browser.

Updated 4 min read By CodingEagles
Free tool OBJ Viewer Open and inspect .obj 3D models. Open tool

An OBJ file is one of the oldest and most widely supported 3D formats. It stores a model’s geometry, its vertices, faces and texture coordinates, as plain text, and is exported by almost every 3D tool. You can open and inspect one in the OBJ viewer without any software.

Here is what an OBJ is and how to work with it.

A plain-text description of a model

Open an .obj in a text editor and you will see lines of coordinates and face definitions. That simplicity is its strength: because the format is open and easy to read, nearly every modelling program can import and export it, which makes OBJ a reliable way to move a model between two tools that otherwise share nothing.

The MTL companion

An OBJ on its own holds only geometry. Colours and materials are stored separately, in a .mtl (material) file that the OBJ references, and that .mtl may in turn point to texture images. So a textured OBJ usually arrives as a small bundle: the .obj, an .mtl, and some images.

That is why, when you open just the .obj, the model appears in a neutral shaded material. The geometry, scale and triangle count are all accurate; the textures simply are not part of that single file.

What OBJ is good for

  • Exchanging models between different 3D applications.
  • Archiving geometry in a simple, durable, human-readable format.
  • Static models where animation is not needed (OBJ does not store animation or rigging).

For real-time and web use, a format like GLB is usually a better fit, as covered in GLB vs glTF.

Open and inspect one

To look at an OBJ, drop it into the OBJ viewer. You can rotate, zoom and pan, switch to wireframe to study the mesh, read the dimensions and triangle count, and save a screenshot, all in your browser, with the file staying on your device.

Frequently asked questions

What program opens an OBJ file?
Almost every 3D modelling tool opens OBJ, since it is one of the most widely supported formats. But to simply look at one, you don't need any of them, the OBJ viewer here opens it in your browser, with nothing to install and nothing uploaded.
Why does my OBJ come with an MTL file?
OBJ stores only geometry. Material and colour information lives in a companion .mtl file, which in turn may reference texture images. So an OBJ often travels as a small set of files. The geometry opens fine on its own; the materials need the .mtl alongside it.
Can OBJ store colour and textures?
Indirectly. The OBJ itself holds geometry and texture coordinates, while the actual materials and image textures sit in the linked .mtl and image files. Open the OBJ alone and you see the shape in a neutral material; the textures require the companion files.

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Related guides

GLB, STL, OBJ & PLY: 3D File Formats Explained What GLB, glTF, STL, OBJ and PLY are each for, and when you'll meet them, so you know which is which. GLB vs glTF: What's the Difference? Same format, two containers: GLB packs everything into one binary file, glTF is text that often links to others. When to use each.