OBJ Viewer

Open a Wavefront OBJ file in your browser with its materials and textures. An OBJ keeps its colours and texture names in a separate .mtl file, and the textures are image files again; select them all together, drop the folder or click Open a folder, and the viewer matches the names the .mtl asks for. Anything missing is listed by name, and the model still opens in grey. Every object and group in the file gets its own line, so you can show or hide parts, and you can switch between the file’s normals, flat (faceted) and smooth shading. OBJ files have no units, so the size is shown in millimetres and inches with a units chooser and a hint when the size looks unlikely. Turn on wireframe, a grid or the bounding box, then save the view as a PNG. Nothing is uploaded.

100% private — everything runs in your browser. Everything runs in your browser; your model files are never uploaded.

How to open an OBJ file online

1. Select the .obj with its .mtl and texture images (or open their folder), or click Try a sample.
2. Check Files the model refers to: the .mtl and every texture are found or listed as missing.
3. Show or hide objects and groups under Parts; pick flat or smooth shading.
4. Check the size under the view (change Units if needed), then save the view as a PNG.

What you can use it for

• Check an OBJ from a 3D shop or a scan before using it
• See whether an OBJ’s materials and textures come through
• Find which texture file an OBJ’s .mtl is missing
• Look at each part of a model on its own
• Measure an OBJ in millimetres or inches before 3D printing
• Save a picture of a model for a client or a listing

The files that make up an OBJ

File	What it holds	In the sample
.obj	Vertices, texture coordinates, normals, faces, objects and groups	48 vertices, 48 texture coordinates, 2 objects
.mtl	Named materials: colours and the texture file names	Checker, Red (mtllib crate.mtl)
Images (.png, .jpg)	The textures the .mtl names	Checker: map_Kd checker.png; Red: colour only

Computed by the viewer’s own reader from the sample files. Faces with four or more corners are split into triangles for display.

What the sample shows per part

Object	Faces in the file	Triangles drawn
Crate	6	12
Base	6	12

What you can do with a model

Control	What it does
Orbit, zoom, pan	Drag to turn, scroll or pinch to zoom, right-drag (or two fingers) to pan
Look from	Corner, front, back, left, right, top or bottom view
Wireframe, floor grid, bounding box	See the triangles, the size against a grid (square size shown) and the box around the model
Units and up axis	Read the file in mm, cm, m, inches or feet; stand the model on Y or Z
Shading normals	As in the file, flat (faceted) or smooth
Parts	Show or hide each object, group or mesh
Save view as PNG	The current view at the view size or twice that, background optional

Units: why an OBJ can look the wrong size

Units in the file	1 unit =	A 20-unit cube is
Millimetres	1 mm	20 mm
Centimetres	10 mm	200 mm
Metres	1000 mm	20,000 mm
Inches	25.4 mm	508 mm
Feet	304.8 mm	6,096 mm

The OBJ format stores numbers only. Most 3D printing models use millimetres, so that is the default; many 3D programs export in metres or centimetres.

Next steps

Print the model: OBJ to STL converts it with units and Y-up fixed, and the STL viewer checks it is watertight. For a flat technical drawing use Orthographic Drawing, or price a print with the 3D Print Cost Calculator.

Sources

Sources: Library of Congress: Wavefront OBJ File Format (OBJ and its MTL material file).

Frequently asked questions

Do I need the .mtl file?

Only for colours and textures. Without it the shape opens in grey and the viewer names the .mtl the OBJ asks for. Add the .mtl (and its images) together with the .obj to see the materials.

How do I open an OBJ with its textures?

Select the .obj, the .mtl and the image files together, or click Open a folder. Texture names in the .mtl are matched by path first and then by file name, so textures in a sub-folder are found too.

Why does my OBJ look grey?

The .mtl file or its textures were not added, or the .mtl names a texture file that is not there. The list of files the model refers to shows what is missing.

How big is my OBJ?

OBJ files store plain numbers with no unit. The viewer reads them as millimetres and shows the size in mm and inches; if the model was made in metres or inches, change Units in the file. A hint appears when the size looks too small or too large.

What are groups and objects?

An OBJ can split its faces into named objects (o) and groups (g). Each one gets a line under Parts with its triangle count, and a tick box to show or hide it.

Flat or smooth shading?

As in the file uses the normals stored in the OBJ (or flat ones if it has none). Flat shows every face; Smooth averages the shading across shared corners, which suits curved scanned or sculpted models.

Can I save a picture of the model?

Yes. Turn the model to the view you want and click Save view as PNG: at the view size or twice that, with a transparent background if you choose it.

Is it free?

Yes. There is no sign-up, no watermark and no file limit beyond what your device can hold.

Are my files uploaded?

No. The model and its files are read by JavaScript in your browser and never leave your device. Only the 3D engine (three.js) is downloaded from a public CDN. A texture that points to a web address is not fetched: it is listed and shown in grey.