PLN File Documentation

Summary

A ArchiCAD Project File is an Archicad solo (single-user) project — a complete BIM building model created in Graphisoft Archicad, holding the 3D model plus all 2D floor plans, sections, elevations and documentation in one file. Its MIME type is application/octet-stream. It opens only in Archicad, which is paid professional software. To view one without Archicad, ask the author to publish it as a free BIMx model, a PDF, or a DWG/IFC export. PLN is version-specific: a newer Archicad’s file will not open in an older one.

Technical details

FeatureValue
Full nameArchiCAD Project File (Archicad solo project)
File extension.pln
MIME typeapplication/octet-stream
Format typeProprietary binary BIM project (single-user)
DeveloperGraphisoft
IntroducedArchicad first released 1987; .pln the long-standing solo format
Contains3D model, 2D views, layouts/sheets, schedules, settings — one file
Single-user vs sharedSolo .pln; Teamwork uses BIMcloud/.plp; archive is .pla
Magic numberNone publicly documented (proprietary version-specific container)
Version lockYes — older Archicad cannot open a newer file; Save As down-versions one release
Open standardNo — proprietary; use IFC for open BIM exchange
PlatformsWindows and macOS (native)
Free viewerNone for raw .pln; BIMx viewer opens a published .bimx
EditorGraphisoft Archicad (subscription/licensed; free education & demo)
Export targets.pdf, .dwg/.dxf, .ifc, .bimx, image, 3D formats
Related extensions.pla, .mod, .gsm, .bimx, .ifc, .dwg
Specification URLgraphisoft.com/solutions/archicad

What is a PLN file?

A .pln is the native “solo project” file of Archicad, the BIM (Building Information Modeling) application Graphisoft has developed since 1987, making it one of the earliest BIM tools. A single .pln contains an entire single-user building project: the 3D building model, every 2D view derived from it (floor plans, sections, elevations, details), schedules, layouts and drawing sheets, view settings and project preferences, all in one file. It is the architect’s working master file, and its closest analogue in the Autodesk world is the Revit project file .rvt.

An older description you may still see claims a .pln holds “only references to objects, not the objects themselves.” That is misleading. The .pln embeds the model and its documentation; what it references externally is loaded library parts (doors, windows, objects from GDL libraries). The format is proprietary, binary and version-specific, and Graphisoft does not publish its internal layout, so this article stays honest about what is publicly known: how a solo project differs from an archive, why the format is version-locked, and how to get a building out of a .pln when you do not have Archicad.

What a solo project file contains

A .pln is a complete project, not a single drawing. It bundles the model and everything generated from it into one document.

.pln (Archicad solo project)
 ├─ 3D BIM model          walls, slabs, roofs, objects as intelligent elements
 ├─ 2D documentation      floor plans, sections, elevations, details from the model
 ├─ layouts & sheets      drawing sheets prepared for printing/publishing
 ├─ schedules & data      quantities, element properties, zone/room information
 ├─ library part refs     doors/windows/objects loaded from GDL libraries (.gsm)
 └─ view & project settings   view maps, attributes, layers, preferences

The one part that lives outside the file is the library parts (.gsm objects). A .pln references these from loaded libraries rather than embedding them, which is why a project opened on a machine without the right libraries can show “missing” objects. This is the practical reason the .pla archive format exists: a .pla bundles all the linked libraries inside one file, so it is the safer choice when sending a project to someone else.

Solo versus Teamwork, and PLN versus PLA

Archicad separates two ways of working. A solo project is a single .pln edited by one person. Teamwork is a shared model hosted on BIMcloud, where many people edit reserved parts of the same project; that shared project is not a .pln. Within solo work, the important distinction is between the .pln and the .pla: the .pln is the working file, while the .pla “archive” additionally packs the linked libraries inside, making it self-contained for transfer. If you are sending a project to a collaborator, sending the .pla avoids the missing-objects problem that a bare .pln can cause.

Version lock and the “won’t open” problem

Like every native BIM authoring format, a .pln is tied to the Archicad version that saved it. A newer Archicad opens older files, but an older Archicad cannot open a file from a newer version. Archicad’s Save As can down-save, but historically only to the immediately previous version (writing that version’s file format), so a large version gap cannot be bridged by saving down once. This makes version mismatch the most common reason a .pln refuses to open. The fixes are specific: use the same or a newer Archicad, ask the author to re-save the project in your version, or move the model through a neutral exchange format such as IFC or DWG. This is a property of the format, not a sign of a damaged file.

Viewing a PLN without Archicad: BIMx, not a “viewer”

There is no free standalone .pln viewer, and searches promising a “free PLN viewer” generally lead to adware rather than a real tool. The honest, supported route for someone without an Archicad license is to have the author publish the project into something openable. The main option is BIMx, Graphisoft’s free hyper-model viewer for desktop, iOS and Android: the author publishes a .bimx from the project, and anyone can then explore the building in 3D with hyperlinked 2D drawings, at no cost. For static output, the author exports PDFs of the drawings or a DWG/IFC of the model. Note the important caveat: BIMx opens a published .bimx, not the raw .pln itself.

Getting the model out: PDF, DWG, IFC and BIMx

Everything below is done from inside Archicad, because the format is proprietary and no third-party tool converts a raw .pln. For drawings, use Publish or Save As to write the layouts to PDF. For CAD collaborators, Archicad exports 2D (and 3D) to AutoCAD DWG/DXF through a translator; geometry transfers but the native BIM intelligence does not. For moving the actual building model into another BIM tool (Revit, Tekla, Solibri), export to IFC, the open buildingSMART interchange standard, which preserves model objects and data far better than DWG. There is no direct .pln-to-Revit converter, and Revit cannot open a .pln; IFC is the bridge between the two systems, and it is a lossy exchange, so parametric behaviour has to be rebuilt on the far side.

Not every PLN is an Archicad project

The .pln extension is shared with an unrelated format: Microsoft Flight Simulator, FSX and Prepar3D save flight plans as XML-based .PLN files, which are plain text and have nothing to do with architecture. Some older CAD tools also used .pln for their own drawing files. If a .pln is small and opens as readable XML, it is almost certainly a flight plan rather than an Archicad project, which is a large proprietary binary.

Frequently asked questions

How do I open a PLN file without Archicad?

There is no free standalone .pln viewer. Ask the architect to publish the project as a BIMx model (free BIMx viewer on desktop and mobile), or to export PDFs of the drawings and a DWG or IFC of the model. Those you can open without Archicad.

Why won’t my PLN file open?

Most often a version mismatch: the file was saved in a newer Archicad than yours, which older versions cannot open, and Archicad down-saves only one version at a time. Use the same or newer Archicad, or ask for a re-save or an IFC/DWG export.

What is the difference between PLN and PLA files?

A .pln is the solo project. A .pla is an Archicad archive that also bundles all the linked libraries inside one file, so it is the safer choice for sending a project to someone without producing missing objects.

References