What is an IFC file?

An IFC file (Industry Foundation Classes) is an open, vendor-neutral format for exchanging BIM models between software. It stores a building or infrastructure project as structured data — every wall, door, beam and duct with its geometry, properties and relationships — in a way any compliant application can read, no Autodesk or Graphisoft license required.

That neutrality is the whole point. A structural engineer working in Tekla, an architect in ArchiCAD and a contractor checking clashes in Solibri or BIMcollab Zoom can all work from the same .ifc file. The standard is maintained by buildingSMART International and published as ISO 16739, which is why public clients in Norway, Denmark, the Netherlands, the UK and a growing list of other countries require IFC deliverables on public projects.

If you just received an .ifc and need to look inside it right now: drop it into our free online IFC viewer — it runs in your browser and the file never leaves your machine. The rest of this guide explains what you are looking at.

What's actually inside an IFC file

Open an .ifc in a text editor and you will find plain text in STEP encoding (ISO 10303-21). Millions of numbered lines, each one an entity:

#137= IFCDOOR('1F6umJ5H93$wM4zt3lXaFV',#42,'Door M_Single-Flush',$,
  'M_Single-Flush:0915 x 2134mm',#136,#132,'259776',2134.,915.);
#154= IFCPROPERTYSINGLEVALUE('FireRating',$,IFCLABEL('EI30'),$);

Four kinds of information hang off those lines:

Semantics. Every object declares what it is — an IfcDoor, an IfcWall, an IfcFlowSegment. A viewer doesn't guess that a shape is a door from its geometry; the file says so. This classification is what makes model checking, quantity takeoff and facility management possible.

Geometry. Shapes come as extrusions, boundary representations or triangulated meshes, placed in a coordinate hierarchy (site → building → storey → element). Geometry in IFC is intentionally "frozen": it describes the result, not the parametric recipe that produced it.

Properties. Data lives in property sets (Psets). Standard ones are defined by the schema — Pset_WallCommon.FireRating, Pset_DoorCommon.IsExternal — and authoring tools add custom ones on top (Revit shared parameters, ArchiCAD classifications). Quantity sets (Qto_…) carry areas, volumes and lengths for estimating. You can browse all of this without any 3D at all in the IFC properties explorer, or export the whole model to Excel — one sheet per class, one column per property.

Relationships. The quiet superpower. IFC records that this door is hosted by that wall, that these spaces form the second floor, that this pump belongs to that system. Roughly a third of a typical file is relationship entities — it's a graph database in a trench coat.

IFC vs RVT vs DWG

The three formats answer different questions, and most exchange problems come from treating them as interchangeable:

The full comparison — including what actually survives each conversion — is in IFC vs RVT vs DWG: what's the difference?, and if you need to move an IFC into editable Revit or DWG, read how to convert IFC without losing data first.

IFC versions: 2x3, 4 and 4x3

Three schema versions matter in practice. IFC2x3 (2006) remains the default exchange currency of the industry — old, but every tool reads it well. IFC4 fixed long-standing geometry and property limitations and is the version certified for new workflows. IFC4x3 (2024) extends the schema beyond buildings to roads, rail, bridges and ports. Your choice is usually dictated by the weakest tool in the chain; when you have the choice, prefer IFC4. The trade-offs are unpacked in IFC2x3 vs IFC4 vs IFC4x3.

Alongside versions there are Model View Definitions (MVDs) — agreed subsets of the schema for a purpose. IFC2x3 Coordination View 2.0 is the classic for design coordination; IFC4 splits it into Reference View (lightweight, for viewing and checking) and Design Transfer View (richer, for taking geometry onward). When someone says "the IFC is wrong", the first question to ask is which MVD it was exported with.

How to open an IFC file

You never need paid software just to look at an IFC:

In your browser (fastest)

A browser-based viewer opens the file instantly with nothing to install. Ours parses the model locally with WebAssembly — open your IFC file here, navigate the spatial tree, click any element for its properties, cut sections and measure. Because nothing is uploaded, it's safe for models under NDA. Works with .ifc and .ifczip, IFC2x3 through IFC4x3.

On the desktop

BIM Vision and Open IFC Viewer are capable free installs; Solibri Anywhere covers viewing with some checking. Worth it if you review models daily or work offline — we compared the field honestly in the best free IFC viewers.

In authoring tools

Revit, ArchiCAD and Tekla all import IFC, but that is the heavyweight option: slow on big files, and the import converts elements rather than editing them natively. If you don't have those licenses, see how to open IFC without Revit.

Getting data out of an IFC

Viewing is half the story; most real tasks are about extraction. Quantity surveyors pull Qto_ sets into estimates. BIM managers audit whether the BEP-mandated properties actually made it into the deliverable. Facility teams build asset registers from spaces and equipment. All of that is spreadsheet work — our IFC to Excel converter flattens the model into one .xlsx with a sheet per class. For the web, gaming or Blender, converting IFC to glTF strips the database and keeps the geometry at a fraction of the size. And when the export from Revit is the problem rather than the file, these export settings fix most of it.

What IFC is not

Honesty helps here. IFC is not a live editing format — you don't "work in IFC", you exchange through it. Round-tripping (IFC → Revit → IFC) degrades data and nobody serious recommends it. Exports are only as good as the settings and mapping used to produce them, which is why the same model can produce a great IFC from one office and a hollow one from another. And the files are big: text encoding plus full relationship data means a 40 MB RVT can become a 100 MB IFC. None of this is fatal. It just means IFC plays the role of the neutral, audit-friendly deliverable — the PDF of BIM, but one you can query.

That query-ability is why the format keeps winning: an IFC you receive today will still open in twenty years, in tools that don't exist yet, without a subscription. For a format born in 1996, that's aging well.