How do I check which IFC version a file uses?

Read the FILE_SCHEMA line in the file header — it says IFC2X3, IFC4 or IFC4X3. Any decent viewer surfaces it too; ours shows a schema badge the moment the model loads, and even a text editor works since IFC is plain text.

Is IFC4 backwards compatible with IFC2x3?

No. They are different schemas: entities were added, removed and restructured between them. Most viewers read both, but a tool expecting IFC2x3 Coordination View may refuse or mangle an IFC4 file. Compatibility comes from the receiving software supporting both schemas, not from the schemas themselves.

Should I export IFC2x3 or IFC4 from Revit?

Check what the receiving tools and the BEP require first — if IFC2x3 CV2.0 is mandated, that settles it. Free choice? IFC4 Reference View for coordination: better geometry fidelity and cleaner property definitions. Revit's IFC4 export has matured to solid.

What is IFC4x3 used for?

Infrastructure. IFC4x3 (ISO 16739-1:2024) adds alignments, earthworks, roads, rail, bridges and ports — assets IFC2x3/IFC4 could only fake with proxy elements. For buildings it adds little; for a highway or rail project it's the only IFC that can model the asset properly.

Can I convert an IFC2x3 file to IFC4?

Not with a simple 'save as' — entities map differently between schemas, so real migration needs IfcOpenShell-based tooling or re-export from the authoring model. In practice the source model is re-exported with IFC4 settings; converting the IFC itself is a last resort when the native model is gone.

IFC2x3 vs IFC4 vs IFC4x3: which version should you use?

Updated July 7, 2026 · IFCfiles team

IFC2x3 vs IFC4 vs IFC4x3 — timeline of the IFC schema versions

Short version: use IFC2x3 when a receiving tool or the BEP demands it, IFC4 when you have the choice, and IFC4x3 when the asset is infrastructure. The long version explains what actually changed between them — because "newer is better" is only half true in openBIM, and the industry's most-used version is two decades old for reasons that aren't laziness.

Timeline of IFC versions: IFC2x3 (2006), IFC4 (2013) and IFC4x3 (2024) with their key differences — Two decades of IFC in one line — and why 2006 still ships more files than 2024.

IFC2x3: the incumbent (2006)

IFC2x3 TC1 is still what most of the world exchanges. Twenty years of implementations mean its behavior is thoroughly known: every authoring tool exports it, every checker reads it, and its Coordination View 2.0 MVD is the certified baseline that tools like Solibri and Navisworks were hardened against. When a government mandate or a BEP says "IFC", unqualified, it usually still means IFC2x3 CV2.0.

Its age shows in specific places: geometry is limited to older representation types (larger files, coarser curved shapes), property templates are looser (vendors invented their own dialects), and there is no real support for anything outside buildings. Reliable, ubiquitous, dated.

IFC4: the current standard for buildings

IFC4 (2013, refined through Add2 TC1) is the version buildingSMART certifies new software against. What changed that you'll actually notice:

Better geometry. Native NURBS and tessellated representations — curved facades and complex shapes export smaller and truer than IFC2x3's approximations.
Cleaner data model. Standardized property templates, base quantities (Qto_ sets) properly defined — takeoffs get more consistent across authoring tools.
Purpose-built MVDs. CV2.0 split into Reference View (lightweight, for viewing/checking — what you want 95% of the time) and Design Transfer View (richer, for taking geometry onward into another authoring tool).
Real MEP coverage. Systems, ports and distribution elements that IFC2x3 modeled vaguely.

The historical objection — "IFC4 exports are immature" — has mostly expired: Revit, ArchiCAD and Tekla all ship certified, solid IFC4 export today. The remaining friction is downstream, in older pipelines and conservative BEPs.

IFC4x3: IFC leaves the building (2024)

IFC4x3 is IFC4 extended to infrastructure: alignment-based geometry (chainage along a road or track), earthworks, bridges, rail, ports and waterways. It became ISO 16739-1:2024, and national road/rail authorities (Scandinavia and the Netherlands first, as usual) are already writing it into requirements.

Two honest caveats. For pure building projects it changes little — don't switch for novelty. And tool support is still uneven: authoring exports exist (Civil 3D, OpenRoads, Tekla), but plenty of viewers and checkers haven't caught up. Test your chain before committing a deliverable to it. (Ours reads all three versions — the schema badge appears the moment you drop the file in the viewer.)

IFC viewer status bar with the detected schema version badge (IFC4) after loading a model — Fastest version check there is: the schema badge in the viewer's status bar.

The differences that matter, in one table

	IFC2x3	IFC4	IFC4x3
Year / status	2006 · de-facto default	2013 · certified standard	2024 · ISO, adoption growing
Tool support	Universal	Broad and mature	Growing, uneven
Geometry	Legacy types only	+ NURBS, tessellation	+ alignment/linear placement
Scope	Buildings	Buildings (better MEP)	+ roads, rail, bridges, ports
Key MVDs	Coordination View 2.0	Reference View, Design Transfer View	Reference View 4x3

Choosing in practice

The version is only half the decision — the MVD is the other half, and mismatched MVDs cause more support tickets than mismatched versions. A sane default policy:

BEP or receiving tool mandates a version → that version. Interoperability beats elegance.
Building project, free choice → IFC4 Reference View.
Geometry continues into another authoring tool → IFC4 Design Transfer View, expectations managed (see what survives conversion).
Infrastructure → IFC4x3 — after a pilot file through the whole chain.

Whatever you export, audit it once before it leaves the office: check the schema badge and click through key elements in the viewer, then scan the Psets in the properties explorer — version arguments dissolve quickly when you can see what the file actually contains. Exporting from Revit specifically? The settings that make or break the file are in how to export Revit to IFC correctly, and the basics of the format live in what is an IFC file?