Free Online U3D / 3D PDF Viewer (No Signup)
Also opens DWG, DXF, STEP, IGES, IFC, SKP, STL, OBJ, GLB, FBX, 3DM and other 3D/CAD files. Drop any file on the viewer.
Works directly in Chrome, Firefox, Safari, and Edge
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What Is an U3D / 3D PDF File?
U3D (Universal 3D) is an open format, standardised as ECMA-363, for compact 3D models. A U3D file is a sequence of blocks: nodes arranged in a tree (groups and models, each with a transform to its parent), mesh generators whose triangles are stored with their positions and normals, and the shaders and materials the models are drawn with. It is best known as the model a 3D PDF carries: Acrobat shows a PDF page with a 3D annotation as a rotatable model, and CAD, BIM and steel-detailing tools such as Tekla and Revit publish to it.
A 3D PDF opens on a page that is nothing but the model, and a viewer that only reads the page shows a blank sheet. This viewer finds the U3D stream inside the PDF, reads which axis the PDF’s saved views call up, and draws the model upright. A PDF in which the model is only a small part of the file, such as a datasheet with one 3D view, still opens as the document.
Meshes are rebuilt with one vertex for every distinct combination of position and normal, so the hard edges of a CAD part stay hard, and progressive-resolution meshes are decoded to their full detail. The model exports to GLB, OBJ, STL and the other formats in the Export menu. Ordinary PDFs open in the PDF viewer.
Who Uses U3D / 3D PDF Files?
Engineers and fabricators who receive a 3D PDF of a part or an assembly instead of a CAD file, steel detailers and contractors reviewing a Tekla or Revit publish, product teams that send 3D technical documentation, and anyone holding a PDF that Acrobat shows as a model and their own PDF reader shows as a blank page.
Common Use Cases
- Look at a 3D PDF on a phone or in a browser, without Acrobat
- Turn a model out of a 3D PDF to GLB, OBJ or STL for a render or a print
- Check the parts of a published assembly in the object tree and hide the ones in the way
- Open a bare .u3d file saved from a CAD or modelling tool
- Measure a part published as a 3D PDF
- See what a 3D PDF holds before forwarding it
Features
U3D Files and 3D PDFs
A bare .u3d opens, and so does a PDF whose pages are a U3D model, which most PDF readers show as a blank sheet.
Every Mesh in Place
The node tree is followed, so each model is drawn at the position, rotation and scale its parents give it.
Hard Edges Stay Hard
Meshes keep a vertex for each distinct position and normal, so the edges of a CAD part are not smoothed away.
Full-Detail Meshes
Progressive meshes are refined all the way to their finest level.
Material Colours
Diffuse colour, emissive colour, reflectivity and opacity come from the shaders and materials the file stores.
Upright From the PDF’s Views
U3D has no up axis, so a 3D PDF is turned using the axis its saved views imply.
Only Real Models
A datasheet with one small 3D view still opens as the document. A PDF that is mostly model opens as the model.
Object Tree
Parts stay grouped as the file arranges them, so you can hide the ones in the way.
Convert to GLB, OBJ or STL
Save the model as GLB, OBJ, STL, FBX, 3MF, USDZ, STEP or DXF, or the view as PDF, PNG or JPG.
Nothing Is Uploaded
The file is read and drawn entirely in your browser. No account, no upload, no copy of your model on a server.
Share and Embed
Send a link that opens the model in any browser, or drop the viewer into your own page with one iframe.
Compatibility & Format Notes
Read: U3D files and the U3D streams of 3D PDFs (found by their stream dictionary, compressed or not). Node trees with several parents, model nodes with their transforms, triangle meshes with normals, the base mesh and the progressive refinements of continuous-level-of-detail meshes, diffuse, emissive and reflectivity material values, and opacity.
Orientation: U3D has no up axis of its own. For a PDF the viewer takes the axis from the saved 3D views; a bare .u3d is drawn Y-up. Units are not stored in the file, so the size is shown as modelled.
Not drawn: models stored as PRC rather than U3D (the other encoding a 3D PDF can hold), textures, lights, line and point sets, animation, and the JavaScript and view-state of the PDF. An encrypted PDF is left to the document reader.
Embed on Your Website
Add this viewer to your own site with a single line of HTML. Click Embed in the toolbar to generate an embed code, or use the snippet below with your own file URL.
Your Files Stay on Your Computer
Your U3D / 3D PDF files are parsed entirely in your browser. Nothing is uploaded, stored, or shared unless you explicitly click the Share button. Shared files are hosted for 90 days then deleted.
Frequently Asked Questions
▶How do I open a 3D PDF without Acrobat?
Drop the PDF on the viewer on this page. If it carries a U3D model, it opens in 3D that you can orbit, with the object tree and layers, in any browser and on a phone. Nothing is uploaded.
▶My PDF opened as a document, not a model. Why?
Either the PDF holds only a small 3D view among ordinary pages, so it is read as the document it mostly is, or the 3D data is PRC, which this viewer does not read, or the PDF is encrypted. A PDF whose pages are the model and nothing else opens as the model.
▶Why is my model lying on its side?
U3D does not say which way is up. For a 3D PDF the viewer uses the axis that the PDF’s saved views imply; a bare .u3d is drawn with Y up, which CAD files that use Z up will not match. Rotate the model with the Edit menu if it still sits wrong.
▶Can I get the model out of a 3D PDF?
Yes. Open the PDF, then use Export to save it as GLB, OBJ, STL, PLY or another format. The meshes keep their material colours and their place in the assembly.
▶Is this U3D viewer really free?
Yes, completely free. No signup, no watermarks, no file size limits on the viewer (the optional share-link feature has a 100 MB upload cap). Built by Innerscene as a tool for architects, engineers, and designers.
▶Are my files uploaded to a server?
No. All parsing, rendering, and conversion runs in your browser: nothing is uploaded, stored, or transmitted by default. The Share button is the only feature that uploads a file, and only when you explicitly click it.
▶Can I convert to another format?
Yes. Click Export in the toolbar to save as STL (3D printing), OBJ (Wavefront), GLB (glTF binary), or PDF (snapshot of the current view).
▶Can I embed this viewer on my own site?
Yes. Click Embed in the toolbar to generate a one-line <iframe> snippet you can paste into any HTML page. You can choose whether the embed shows the viewer’s toolbar.
Acrobat and Adobe are trademarks of Adobe Inc.; Tekla is a trademark of Trimble; Revit is a trademark of Autodesk, Inc. Innerscene is not affiliated with any of them.