What is the PLN file format?
.pln file extension is used by Archicad, Graphisoft's architectural BIM software. A .pln file contains an Archicad Solo Project, which comprises elements such as a 3D model, lines, objects, calculations, and other BIM and CAD data.
Usage of .pln files
.pln files are used by architects and designers for storing building structure models, interior and exterior designs, and construction plans. The format is the standard single-user project file in Archicad, as opposed to the teamwork archive format .pla, which bundles the project together with embedded library content for sharing or long-term archiving.
.pln - a format unique to Archicad
.pln is a proprietary binary format developed specifically for Archicad to support functionalities such as the embedded CineRender engine (powered by MAXON's Cinema 4D renderer) for photorealistic visualization, advanced geometrical models, 2-point perspective, and full BIM data including quantities, structural layers, and material schedules. Files are version-specific: a project saved in a newer release may not open in older versions of Archicad.
Archicad library components are stored separately as .gsm objects. For collaboration or delivery, projects can be exported to the open IFC standard or published as .bimx files for mobile viewing.
Security & safety
RISK: LOWAn .pln is BIM project data, not an executable, so opening it in Archicad is safe. The realistic concerns are non-malware: a .pln may rely on external libraries (.gsm) that, if missing, show as 'missing' objects - which is why authors send the self-contained .pla archive for transfer; and a building model can contain confidential project/client information, so treat shared files as sensitive. Download Archicad and BIMx only from graphisoft.com to avoid bundled-installer and fake-viewer sites (no legitimate free standalone '.pln viewer' exists - beware those download lures).
Format details
in a nutshell- Microsoft Flight Simulator / FSX flight plan - MSFS, FSX and Prepar3D save flight plans as XML-based .PLN files (text, unrelated to Archicad).
- DesignCAD / generic CAD plan - Some older CAD tools used .pln for their own drawing/plan files.
Programs that open PLN files
Windows2 apps
Graphisoft Archicad
Paid File > Open the .pln. Editing/viewing the real model requires Archicad (subscription/licensed; free education & demo versions exist).
BIMx (Graphisoft)
Free Not for .pln directly - ask the author to publish a .bimx from the project; then open that free in BIMx desktop to walk the model and view linked drawings. 
macOS2 apps
Graphisoft Archicad
Paid File > Open the .pln; Archicad has a native macOS build (Graphisoft is historically Mac-strong). 
Android1 app
BIMx (iOS app)
Free Open a published .bimx model to explore the building in 3D with hyperlinked 2D drawings on iPhone/iPad. Technical details
deep spec| Developer | Graphisoft SE |
| Primary application | Archicad (Windows and macOS) |
| Format class | Proprietary binary BIM project container |
| User mode | Single-user (Solo) project; not for multi-user Teamwork sessions |
| File scope | Complete Archicad project: 3D model, 2D drawings, views, layouts, schedules, and settings |
| Version compatibility | Version-specific; files saved in a newer Archicad release cannot be opened in older versions |
| Library dependency | References external .gsm library objects; components are not embedded by default |
| Archive counterpart | .pla format bundles project together with its library for self-contained distribution or archiving |
| Rendering support | Embeds CineRender engine (based on MAXON Cinema 4D) for photorealistic visualization inside Archicad |
| BIM data stored | Element properties, quantities, structural layers, material schedules, and IFC classification data |
| 2D/3D integration | Single file holds both 3D geometry and associated 2D floor plans, sections, and elevation drawings |
| Export paths | Can be published to IFC, DWG, PDF, BIMx (.bimx), and various image formats from within Archicad |
| MIME type | application/octet-stream |
| Platform support | Windows and macOS; no native Linux version of Archicad |
| File identification | No publicly documented constant magic bytes; identified by .pln extension and Archicad file origin |
| Released | 1987 (Archicad/Graphisoft); .pln the solo project format for decades |
| Specification | graphisoft.com |
PLN conversions
Community Q&A
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