STL viewer online — open .stl files with dimensions, no upload
Open any binary or ASCII STL in your browser and see it with its real dimensions, volume, weight and a watertight check — not just a spinning preview. Measure holes and clearances, cut a cross-section, then repair, scale or slice it. Nothing is uploaded.
Measure
Click a part to isolate it and see its own dimensions.
Dimensions & mass
Load a model to see its dimensions, volume, surface area and mass.
Cross-section
Measuring tips
- Snap is on by default — clicks land on the nearest corner or edge vertex, which is where CAD tessellations keep exact dimensions.
- Hole diameters: click three points spread around the rim (not in a line). The fit is a true 3D circle, so it works on tilted faces too.
- Units: STEP/IGES are read in millimetres from the file. Mesh formats carry no units, so the tool applies each format’s convention — if a model looks 10×, 25×, or 1000× off, switch File units rather than the display unit.
- Mass multiplies the closed-mesh volume by the material density — pick the right material, and expect open or hollow meshes to read low.
- X-ray + cross-section together show internal pockets, wall thickness and hidden holes.
Capabilities
What the stl viewer does
- Instant preview of binary and ASCII STL files with studio lighting, orbit, zoom, pan and X-ray shading — no plugins, no install.
- Bounding-box dimensions, volume, surface area, centre of mass and print weight by material, switchable between mm, cm and inches.
- Watertight check: open edges, non-manifold edges and flipped faces are counted so you know whether the file will slice cleanly — with a link to fix it.
- Point-to-point distance with X/Y/Z deltas, angles and hole diameters; clicks snap to the mesh’s corners and edges.
- Cross-section on any axis with the section outline and area — see walls, pockets and infill-relevant cavities before printing.
- Export to GLB, save an annotated screenshot, and hand the file straight to the repair tool, scale tool or online slicer. 100% private.
Process
How it works
- Drop the STLDrag a .stl file onto the viewer — it loads in your browser in well under a second for typical models.
- Read the numbersDimensions, volume, weight and the watertight verdict appear immediately; switch units if the file was exported in inches.
- Measure and actMeasure what matters, cut a section to check inside, then repair, rescale or slice the model with the linked tools.
Before you print
How to check an STL file before 3D printing
Three things decide whether a download prints well: size, watertightness and units. The viewer shows the bounding box at the top of the panel — compare it with your printer bed, and use Distance to confirm a critical wall or hole. The watertight check counts open and non-manifold edges; a model with holes slices unpredictably, so send it to STL repair first. Finally, if a part that should be 50 mm reads 1.97, it was exported in inches: switch File units to inch here, or fix the file for good with STL scale & units. For filament weight, cost and bed-fit in one verdict, run the printability checker.
Units
STL has no units — what to do when a model looks 25× too small
The STL format stores bare triangles with no unit information, so every program guesses. Slicers assume millimetres; some CAD exports write inches, and a few tools export metres. A model that looks 25.4× too small was exported in inches, one that looks 1000× off in metres. This viewer reads STL as millimetres and lets you switch File units to inch, cm or m — dimensions, volume and mass update instantly — so you can see the intended size before fixing the file.
Notes
Good to know
- STL stores geometry only — no colours, textures, units or part names. Multi-part prints are usually separate files or a 3MF.
- Volume, weight and centre of mass assume a watertight mesh; open meshes are flagged and the numbers are approximate until repaired.
- Very large STLs (millions of triangles) load on desktop browsers but can exceed the memory of a phone.
- Measurements are taken on the triangle mesh; curved surfaces are as accurate as the export resolution.
FAQ
Questions, answered
How do I open an STL file without installing software?
Drop it here. The viewer renders the STL in your browser with WebGL and shows its dimensions, volume and watertight status — no slicer, no CAD program, no account.
Is my STL file uploaded to a server?
No. The file is parsed and rendered on your own device with WebGL — it is never uploaded, there is no account and no watermark. Close the tab and nothing is left behind.
Can I see the dimensions of an STL file?
Yes. The bounding box (X × Y × Z), volume, surface area, centre of mass and weight by material appear as soon as the file loads, in mm, cm or inches, and you can measure any feature with the Distance, Angle and Hole ⌀ tools.
Is my STL watertight / printable?
The viewer counts open edges, non-manifold edges and flipped faces. Zero of each means a sealed mesh that slices cleanly; anything else links you to the STL repair tool, which seals holes in the browser.
Why does my STL load tiny or huge?
STL has no units. A file exported in inches reads 25.4× too small as millimetres; switch File units to inch in the panel, or use the STL scale & units tool to rewrite the file.
Can I convert the STL to another format here?
You can download the model as GLB from the viewer; for OBJ, 3MF, USDZ and other targets use the STL converters.
What is the maximum file size?
Up to 300 MB. Very large meshes (millions of triangles) load on a desktop browser but can exceed the memory of a phone; the closed-mesh check is skipped above 1.5 million triangles to keep things responsive.
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