Open a 3D model, turn it round and measure it.

Open GLB, glTF, STL, OBJ, PLY, 3MF and DAE files in your browser with nothing uploaded: turn them round, cut through them, see their parts and measure them.

By Suraj Kumar3 November 20265 min read

A knot drawn in 3D on a grid, with its size, 52.9 × 26 × 55.2 mm, and the words A closed shape beside it

A 3D file is a list of triangles, and most computers no longer come with a program to show one. KeepSimp's 3D viewer draws it in your browser instead: you turn it round, look inside, see what it is made of and measure it. The file is read on your device and never sent anywhere.

Drop the model on the page.

Open the 3D viewer and drop a file on it, or press Choose a file. It opens GLB and glTF 2.0, STL (binary and text), OBJ, PLY, 3MF and Collada (DAE) files. Squeezed glTF files (Draco, meshopt and KTX2 pictures) open too, with decoders served by KeepSimp itself.

Some models come in several files. An OBJ keeps its colours in a .mtl file and its pictures beside it; a .gltf keeps its data in a .bin. Choose them all at once, and the page says by name if one it needs is missing.

Files that only their own program can read, such as Blender's .blend, SketchUp's .skp or SolidWorks parts, do not open in any browser. The page says which file to export from the program instead.

Turn it round and look inside.

Drag to turn the model, scroll or pinch to zoom, and drag with the right mouse button or two fingers to move it. Fit brings it all back into view, and Front, Top, Side and Corner look at it from those sides. Keys do the same: F fits it, 1 to 4 choose a side.

Cut slices through it across its height, width or depth, and the cut is filled with a flat colour, so walls and hollows show. Under More options it can be drawn as edges, a wireframe, an X-ray, by the way its faces point, or with a checker that shows how pictures are laid on it.

Parts lists every piece by name: hide one, or press it to see where it is. A model's animations play with a timeline, at half, normal or double speed.

Measure it, at its real size.

The size of the box around the model is said first, with its surface area. When the model is a closed shape, every edge joining exactly two faces turned the same way, its volume is given too; when it is not, the page says why, counting the holes and the edges that do not join, and gives no volume, because an open surface has none.

Press Measure, then two points on the model, for the straight distance between them. A press near a corner snaps to it.

STL, OBJ and PLY files do not say what their numbers mean. The page reads STL files as millimetres, as 3D printers and CAD programs write them, and asks you to choose another unit if the size looks wrong. 3MF and Collada files say their unit, and glTF is always in metres.

Save a picture of it.

Picture saves a PNG of the model as it is shown, without the grid or measuring marks. Its size and a clear background are under More options.

Change the format turns the model into GLB, glTF, OBJ, STL, PLY, 3MF or USDZ, says first what each keeps and leaves out, and reads every file back before you get it. Getting a model ready for a 3D printer and making it smaller come in later updates; the page shows them as coming and does not offer them yet.

A little less theory. A little more doing.

Try it on your own terms, with a free browser tool.

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