What is an OBJ file?

An OBJ file is a 3D model in the Wavefront OBJ format, a plain-text list of vertices, texture coordinates, normals and faces. Almost every 3D program reads it. Materials and textures live in a separate .mtl file and image files beside it, and the format has no unit and no animation.

Drop your OBJ file here

Extension	.obj (with .mtl for materials)
Name	Wavefront OBJ
Created by	Wavefront Technologies, for its Advanced Visualizer
Stores	Vertices, UVs, normals, polygons, groups
Materials	In a separate .mtl file
Units	None stored
Opens in	Blender, Maya, 3ds Max, ZBrush, slicers, this page

What is inside an OBJ file

Open an OBJ in a text editor and you can read it. Lines that start with v are vertex positions, vt are texture coordinates, vn are normals, and f are faces that list which vertices they join. Faces can have any number of corners, not only three, which is one reason modellers like it.

A line that starts with mtllib names the .mtl file, and usemtl lines say which material each group of faces uses. The .mtl file in turn names the texture images.

Why the textures go missing

Because an OBJ model is often three or more files, the .mtl or the images get left behind when someone sends only the .obj. The model then opens with no colour. To keep everything in one file, convert to GLB, which packs geometry and textures together.

How to open an OBJ file

Use the viewer at the top of this page to see the shape. Blender, free, imports OBJ with its .mtl and textures if they are in the same folder. Slicers such as PrusaSlicer and Cura also open OBJ for printing.

Free tools for OBJ files

OBJ viewer Open a .obj file and spin it in your browser. OBJ to STL Convert an OBJ to a binary STL for 3D printing. GLB to OBJ Convert a GLB to OBJ geometry for any 3D editor. FBX to OBJ Convert an FBX to OBJ for any 3D editor.

Frequently asked

OBJ or STL for 3D printing?

Both work in most slicers. STL is the safer choice because every printer tool reads it. OBJ is useful when a slicer can use its colours, which some multi-colour workflows do.

Does OBJ support animation?

No. OBJ stores one static shape. For animation, use FBX or glTF (GLB).

Why is my OBJ file so large?

It is plain text, so every number is written out in characters. The same mesh is often three to five times larger than a binary format like GLB or STL. Compressing it as a zip helps a lot.