Open STL files in an interactive 3D view right in your browser - plus OBJ, 3MF, PLY, GLB, AMF and OFF. Check the size, volume and print readiness before you slice, then convert STL to OBJ or GLB without uploading a thing. Model came in a ZIP? Drop it as is, or peek inside with the ZIP Viewer.
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Try a sample
1M+ triangles mm and inches Print checks No upload
ReadBuild meshDisplay
Reading file...0%
model.stl
STL
Open edgesNon-manifoldFlipped
Click two points on the model
Drag to rotate · scroll or pinch to zoom · right-drag to pan
Model info
3D print readiness checking...
Filament estimate
20%
An estimate: about 0.8 mm solid walls plus your infill. Supports, brims and slicer settings change the real number.
Smooth blends faces that meet at less than 30 degrees. Flat shows every triangle - handy for judging mesh resolution before printing.
Sizes in mm: 180 x 180 x 180 (mini printers), 220 x 220 x 250 (the classic bed-slinger), 256 x 256 x 256 and 300 x 300 x 400. The outline turns red when the model does not fit.
Show sizes in
File units (what 1 unit in the file means)
Model 25 times too small? It was saved in inches. 1000 times too small? Metres.
50%
Inside surfaces show in red so the cut is easy to read.
The grid and axes are left out of transparent shots. Need a smaller file for a listing? Try the Image Resizer or PNG to WebP.
Open your model. Drop an STL, OBJ, 3MF, PLY, GLB, AMF or OFF file anywhere on the page, browse for it, paste it, or try a sample. Drop several files or a ZIP to open them all.
Look around. Drag to rotate, scroll or pinch to zoom and right-drag to pan. Jump to the front, top, side or iso view, switch to orthographic, and try wireframe, normals or X-ray mode.
Measure and check. Read the size, volume, surface area and triangle count, measure between two points, slice it with the section plane and see the print checks, build plate fit and filament estimate.
Export or screenshot. Save the model as binary STL, ASCII STL, OBJ or GLB, or take a PNG screenshot of the view with a transparent background.
Mouse, touch and keys
RotateLeft-drag · one finger
ZoomWheel · pinch
PanRight-drag · two fingers
Fit to viewF
Front / side / top / iso1370
Perspective / orthographic5
Auto-rotate / grid / problem edgesR / G / E
Measure / stopM / Esc
How to open STL files on Windows, Mac, iPhone and Android
Every device with a modern browser can open STL files on this page.
Here is what each system offers on its own, and when the browser is the quicker option.
Windows 10 and 11
Some Windows PCs still have Microsoft's 3D Viewer app, which opens STL files, but it is not on every machine. Free slicers such as PrusaSlicer, UltiMaker Cura and Bambu Studio open STL too, though they are big installs just to take a look.
Mac
Select the file in Finder and press Space - Quick Look can preview many STL files. For measurements, print checks or other formats such as 3MF, open the file here instead.
iPhone and iPad
iOS has no built-in STL viewer. Open this page in Safari, tap the drop zone and choose the file from the Files app - rotate with one finger and pinch to zoom.
Android and Chromebook
Android does not open STL files out of the box either. In Chrome, tap the drop zone and pick the model from Downloads or Drive - the same works on a Chromebook.
3D viewer features
Eight formats and ZIPs
STL, OBJ with materials, 3MF, PLY, GLB, glTF, AMF and OFF - drop several at once and switch between them.
Fast with huge meshes
STL, PLY and OFF are read in a background worker, so multi-million triangle scans open without a frozen tab.
Every angle
Orbit, pan and zoom, standard views, orthographic camera, auto-rotate and full screen, with touch gestures on phones.
Four ways to look
Solid with any colour, wireframe, normals and X-ray, flat or smooth shading and four lighting presets.
Measure anything
Size in mm or inches, point-to-point distance and a section plane that slices through the model.
Print readiness
Holes, non-manifold edges and flipped faces drawn on the model, plus a build plate fit check.
Filament estimate
Grams, metres and cost for PLA, PETG or ABS at the infill you pick.
Convert and capture
Export STL, ASCII STL, OBJ or GLB, and save PNG screenshots up to 4x with a transparent background.
Is my STL ready to print?
A slicer needs a closed, watertight skin to tell the inside of a model from the outside.
The viewer welds the triangles together, checks every edge and draws the problems right on the model.
Holes (orange edges) - edges used by only one triangle. Small gaps are usually fixed by the slicer, big ones can leave missing walls.
Non-manifold edges (red) - edges shared by three or more triangles, common when parts are merged without a boolean union.
Flipped faces (purple) - neighbouring triangles that point opposite ways. Turn on Show inside faces in red to see the whole face.
Inverted normals - the normals stored in the file disagree with the triangles, or the whole model is inside out.
Separate parts - several shells in one file. Fine for a multi-part plate, a surprise if you expected one solid.
Size and units - a 0.8 mm figurine was probably exported in inches or metres. Change the file units and check again.
The section plane is the quickest way to check wall thickness and hollow parts. Slide it through the model and the cut faces show up in red.
How to convert STL files
Open the model, then pick an export under the 3D view.
STL to OBJ - for Blender, game engines and most 3D apps.
STL to GLB - for websites, AR previews and online stores. GLB also keeps the colours of a 3MF, PLY or OBJ.
ASCII to binary STL - binary files are about five times smaller and load faster in slicers. The reverse gives you a readable text file.
OBJ, 3MF, PLY, OFF or GLB to STL - for slicers and printers that only take STL.
Need a picture instead? Take a screenshot, then shrink it with Compress PNG or turn it into a JPG with PNG to JPG. Turning a mesh back into an editable STEP file is not possible here - that needs CAD reverse engineering.
Why won't my STL file open?
The viewer names the problem when a file fails.
These are the usual suspects:
The download is a ZIP. Model sites often pack STL files into a ZIP - drop the ZIP here as is, or browse it in the ZIP Viewer.
The file is 0 bytes or cut short. The download or export stopped early. Download it again - the viewer still shows the part that arrived and says how much is missing.
It is not an STL at all. STEP and IGES are CAD files and G-code is printer instructions. Export an STL from the CAD program, or open the STL the G-code came from.
The model looks dark or inside out. Its normals point inwards. The print checks say so, and most slicers fix it on import.
The model is tiny or huge. STL has no units - switch File units to inches or metres.
The phone runs out of memory. Scans with many millions of triangles need a desktop browser. Close other tabs and try again.
STL vs OBJ vs 3MF vs PLY vs GLB
All of them store a model as triangles, but they carry different extras.
Format
Colour and materials
Units
Typical use
STL
None
No (mm by habit)
3D printing, model downloads
OBJ
Yes, in a separate .mtl
No
Exchange between 3D apps
3MF
Yes, plus print settings
Yes
Modern slicers, multi-colour prints
PLY
Per-vertex colour
No
3D scans and point clouds
GLB / glTF
Full PBR materials, textures
Metres
Web, AR, games
OFF
Optional colours
No
Research and geometry tools
Converting for a slicer? Export STL. Sharing on the web or in AR? Export GLB - it keeps the colours.
What is an STL file?
STL is the common language of 3D printing.
It was created by 3D Systems in the late 1980s for its stereolithography printers, and today almost every slicer and CAD program reads and writes it.
An STL file is nothing more than a list of triangles that wrap the surface of an object. There is no colour, no material and no unit, which is why a quick viewer is handy for checking what a file really holds before you print or buy it.
STL comes in two flavours: compact binary (an 80-byte header plus 50 bytes per triangle, so a million triangles is about 50 MB) and readable ASCII text that is several times bigger. This viewer opens both and converts one into the other.
Drop the .stl file anywhere on this page or click to browse. It opens in an interactive 3D view in a second or two - drag to rotate, scroll or pinch to zoom, right-drag or two-finger drag to pan.
Nothing to install, no account, and it works on Windows, Mac, Linux and Chromebooks.
Phones have no built-in STL viewer, but this page works in Safari and Chrome. Tap the drop zone, pick the file from Files or your Downloads, and use one finger to rotate and two to zoom or pan.
Got the model as a ZIP from a download site? Pick the ZIP - every model inside opens.
Binary and ASCII STL, OBJ (with its MTL materials and textures if you pick them together), 3MF, PLY meshes and point clouds, GLB and glTF, AMF and OFF.
STEP and G-code are not meshes, so the viewer explains how to get an STL out of them instead.
Open the model and look at Fits a build plate of - it checks 180, 220, 256 and 300 mm printers, allowing for a 90 degree turn on the bed. Click a size to draw that build volume around the model.
If the model looks tiny or huge, the file was probably saved in other units - switch File units to cm, m or inches and every number updates.
The volume is shown as soon as the model opens. It is the sum of the signed volumes of all triangles - the same method slicers use - and it is exact for closed models.
The filament estimate adds about 0.8 mm of solid walls to the infill you choose and uses the density of PLA, PETG or ABS. Supports, brims and slicer settings change the real number.
The viewer welds the triangles and checks every edge. It counts holes, non-manifold edges (shared by three or more triangles), flipped faces and separate parts, and draws the problem edges on the model in orange, red and purple.
Most slicers repair small problems automatically when you import the file.
Open the model and pick an export: binary STL, ASCII STL, OBJ or GLB. It works the other way too - open an OBJ, 3MF, PLY, OFF or GLB and save it as STL for your slicer.
The conversion runs in your browser and the file downloads straight away.
No. The model is read and drawn by your own browser with WebGL and never leaves your device.
That makes the viewer safe for client work, unreleased products and paid models.
