PRJ Converter
FileFlip converts PRJ files into 14 other formats entirely inside your browser, using Assimp compiled to WebAssembly. The PRJ file is never uploaded to a server: it is read off your disk, converted on your own machine, and saved back by the browser. There is no file-size limit and no account to create.
How do I convert a PRJ file?#
- Drop your PRJ file onto the converter at the top of this page, or click it to pick one from your computer.
- Choose the format you want out of it. FileFlip downloads the engine that conversion needs, once, and your browser caches it.
- Conversion starts the moment you pick the format, and the result is yours to download. The work happens in this tab, so nothing is uploaded and nothing is queued.
Is it safe to convert PRJ files online?#
Yes, because nothing is uploaded. FileFlip converts PRJ files inside the browser tab you already have open, using WebAssembly builds of the same engines a desktop converter would install. Your file is read from your own disk into the page's memory, and no request carrying it is ever made.
You do not have to take that on trust. Open your browser's network panel, run a conversion, and you will see the engine come down and your file go nowhere. There is no upload, no server-side copy, no retention window, and no account tied to what you converted.
How FileFlip works lists every engine, its version and its download size, and shows how to check for yourself that nothing leaves your machine.
What happens to a PRJ file#
FileFlip converts PRJ into 14 formats with Assimp, all of it inside the browser tab. Each conversion below names the engine it uses, what it downloads, and exactly what that conversion keeps or drops.
| Category | 3D Models |
|---|---|
| File extension | .prj |
| FileFlip support | Read only, so it is a source rather than a target |
| Conversions available | 14 |
| Engines | Assimp |
| Downloaded to your browser | 11.2 MB on the first conversion, then cached |
What is a PRJ file?#
A PRJ file from 3D Studio is a project variant of Autodesk's chunk-based 3DS format, the same binary structure with a different top-level chunk marking it as a working project rather than an exported mesh.
Use PRJ only when working directly in original 3D Studio DOS project files rather than their exported meshes.
Convert PRJ to OBJ or glTF to get the mesh into anything modern, since current tools target 3DS or newer formats rather than the old project files.
The PRJ file format reference covers the specification, the programs that open one, and what each conversion keeps or drops.
PRJ questions people ask#
What is a PRJ file from 3D Studio?
A PRJ file is a 3D Studio DOS project, using the same chunk-based structure as a 3DS file but marked as the working project a 3DS mesh gets exported from, rather than the exported mesh itself.
Is a 3D Studio PRJ file the same as an ArcGIS PRJ file?
No, they're unrelated despite sharing an extension. A 3D Studio PRJ file is binary 3D scene data, while GIS software like ArcGIS uses .prj for a plain-text coordinate-system definition. The two need to be told apart by their source, not their extension.
What's the difference between a PRJ and a 3DS file?
Both use 3D Studio's chunk-based format, but a 3DS file is the exported mesh while a PRJ file is the working project, which can carry additional light and camera chunks that a plain 3DS export doesn't.