OBJ Viewer — Open OBJ Files Online

Wavefront OBJ is one of the oldest 3D formats still in daily use. It was created by Wavefront Technologies in the late 1980s for its Advanced Visualizer software, and its specification is open, tiny and stable. Nearly forty years later almost every program that touches 3D can read it, which is why OBJ remains the safest choice when you have no idea what software is at the other end.

An OBJ file is plain text. Each line is a simple statement: v for a vertex position, vt for a texture coordinate, vn for a normal and f for a face. You can open one in a text editor and read it. That simplicity is its strength and its limit — the files are large compared with binary formats, and parsing a big one is slow.

OBJ stores geometry only. Materials live in a separate .mtl file referenced by a mtllib line at the top, and that file in turn points at texture images sitting alongside. An OBJ dropped on its own still renders, just in plain grey, because the material definitions were never in it.

The format has real gaps. There is no animation, no skeleton, no camera or light, and no scene hierarchy beyond named groups. There is also no unit and no declared up-axis, so software has to guess — which is why an OBJ can arrive rotated ninety degrees or a thousand times too large.

Faces may be triangles, quads or arbitrary n-gons, and can carry negative indices that count backwards from the end of the vertex list. Well-formed exports avoid the awkward corners, but files written by older tools sometimes use them, which is a common reason an OBJ opens in one program and not another.