PLA File Documentation

Summary

A PLA (Archicad Archive Project) file is a single, self-contained Archicad project: it bundles the whole BIM model together with every library part, object and texture the model uses, so the project opens on another computer without any “missing library” errors. Graphisoft created the format for Archicad, and only Archicad opens a .pla file directly. Its MIME type is application/octet-stream. If you do not have Archicad, ask the sender for an IFC, DWG, PDF or BIMx export instead.

Technical details

FeatureValue
Full nameArchicad Archive Project
File extension.pla
MIME typeapplication/octet-stream
Format typeSelf-contained binary BIM project archive
DeveloperGraphisoft
ApplicationArchicad (BIM authoring software)
Introduced1990s; current in Archicad 27 / 28
Open standardNo — proprietary Graphisoft format
What it embedsProject data plus all linked libraries, GDL objects and textures
Contrast with.pln (project that references libraries externally)
Version behaviourForward-compatible only (newer Archicad opens older files, not vice versa)
Magic numberNone publicly documented (proprietary binary)
Neutral exportsIFC, DWG/DXF, PDF, BIMx
Related extensions.pln, .tpl, .mod, .gsm, .bimx, .ifc, .pmk
Specificationgraphisoft.com (no public byte-level spec)

What is a PLA file?

PLA is the Archicad Archive Project format from Graphisoft, the maker of Archicad, a BIM (Building Information Modeling) application used by architects. An everyday Archicad project is a PLN file, which references external libraries of objects — doors, windows, furniture, custom GDL parts — that live in separate folders on the machine. A .pla is different: it packs the project and every library part, object and texture the project actually uses into one self-contained file. That is the whole point of the “archive” in the name.

The practical consequence is that a .pla travels well. Send a bare .pln to another office and it may open with “missing library part” placeholders where the linked objects should be; send the .pla and the model arrives complete, because the libraries are inside the file. That makes PLA the format architects reach for when they archive a finished job, hand a project to a consultant, or move work between computers. It is a proprietary binary format, tied to a specific Archicad version, and only Archicad reads it natively.

PLA versus PLN: embedded versus referenced libraries

Understanding PLA means understanding what it is not. The two Archicad project formats differ only in how they treat libraries, and that single difference drives everything about when you use each one.

AspectPLN (standard project)PLA (archive project)
LibrariesReferenced from external folders / BIMcloudEmbedded inside the file
File sizeSmaller (geometry and settings only)Larger (carries all used library parts)
PortabilityBreaks if the recipient lacks the librariesOpens complete anywhere
Typical useDay-to-day editing on a configured workstationSending, archiving, long-term storage

A .pla is not a fundamentally different model; it is the same project data with the library dependencies resolved and baked in. Inside Archicad you can convert freely between the two: Save As a .pla to a .pln to “de-archive” it (the embedded libraries become referenced again), or Save As .pla to bundle a .pln for shipping. Archicad only embeds the parts the project references, so a .pla is not a copy of the entire installed library, just the subset in use.

What a PLA holds: the BIM model and its embedded content

A single .pla stores a complete building information model, not just drawings. The content falls into a few clear groups.

PLA archive project
 ├─ BIM model            3D geometry: walls, slabs, roofs, columns, beams, zones
 ├─ 2D documentation     floor plans, sections, elevations, details, layout sheets
 ├─ Embedded libraries   the GDL objects / library parts the project uses  ← the "archive"
 ├─ Textures & surfaces   materials, surface definitions, fills, line types
 ├─ Attributes            layers, pens, composites, building materials
 └─ Schedules & settings  quantity takeoffs, project preferences, saved views

The elements are parametric. A wall in the model is not a set of lines but an object that knows its composite structure, height, connections and material, which is what separates BIM from plain CAD. The embedded GDL objects (Geometric Description Language, Graphisoft’s scripting language for library parts) are the reason a .pla is larger than the equivalent .pln: each custom object’s definition rides along inside the file so it renders identically on the receiving machine.

A proprietary binary format with no public signature

Archicad’s project formats are proprietary and undocumented. Graphisoft has never published a byte-level specification for .pla, and there is no stable, publicly documented magic number you can rely on to identify one. In practice a .pla is recognised by its extension and its origin (it came out of Archicad), not by a header signature the way a PNG or ZIP file is. It is emphatically not text: open one in a text editor and you get binary noise.

Because the layout is closed, there is no reliable third-party reader. Tools that claim to “open any PLA” without Archicad generally cannot parse the model; at best they read an embedded preview. If you need the data and do not own Archicad, the honest answer is that you must obtain a neutral export (below) rather than crack the file open directly.

Version compatibility: why an old Archicad rejects a new PLA

PLA files are version-tied. Each Archicad release writes its own file structure, and compatibility runs one way only: a newer Archicad opens a .pla saved by an older version, but an older Archicad generally cannot open a project saved by a newer one. This is the single most common reason a .pla “won’t open” — the file came from a later release than the installed program.

There are two fixes. Open the file in the same or a newer Archicad version, or ask the sender to Save As and choose an older version (Archicad can save down a limited number of releases), or to export a neutral format that carries no version lock. For long-term archiving this matters: a .pla kept for a decade may outlive the Archicad version that can read it, which is why an accompanying IFC or PDF export is a sensible archival companion.

Getting data out: IFC, DWG, PDF and BIMx

Most people who receive a .pla do not own Archicad, so the real workflow is to get a neutral export from someone who does. Each target serves a different need.

PLA  →  IFC    open BIM standard; editable in Revit, Tekla, Solibri, BlenderBIM
PLA  →  DWG    2D CAD drawings (and some 3D) for AutoCAD; loses live BIM data
PLA  →  PDF    drawings and layouts for anyone, no CAD software needed
PLA  →  BIMx   free view-only 3D "hyper-model" walkthrough on desktop/mobile
PLA  →  PLN    de-archive back to a standard referenced-library project

IFC (Industry Foundation Classes) is the route to keep editing the model in other BIM software, since it is the open, vendor-neutral BIM exchange standard. DWG gives 2D drawings usable in AutoCAD but flattens the intelligent model into geometry. PDF is pure documentation output. BIMx is Graphisoft’s free hyper-model viewer: publish a BIMx file from the .pla and recipients walk through the building in 3D on a phone or desktop, view-only, without any Archicad license. To move a project into Revit specifically, the path is .pla → IFC in Archicad, then import the IFC into Revit; there is no direct .pla import.

Frequently asked questions

How do I open a PLA file without Archicad?

You cannot open the raw .pla without Archicad — the format is proprietary and has no reliable third-party reader. Ask whoever sent it to export a neutral format from Archicad: IFC to edit in another BIM tool, DWG for CAD, PDF for drawings, or a BIMx hyper-model you can walk through in the free BIMx viewer.

What is the difference between PLA and PLN?

A .pln is the standard Archicad project and references its libraries from external folders. A .pla is an archive that embeds those libraries inside the file, so it opens complete on any machine. Use .pla to send or archive a project, and .pln for day-to-day work on a configured workstation.

Why won’t my PLA open?

Almost always a version mismatch: a .pla saved by a newer Archicad cannot be opened by an older one. Open it in the same or a later Archicad version, or ask the sender to save it down to your version or export it to IFC.

References