IFC 2x3 vs IFC 4: which one should I choose for my audit?
Standards · 7 min · 2026-08-05
A clear comparison between IFC 2x3 and IFC 4 (IFC4): what changed, the advantages of each version, software compatibility and which one is best for auditing your BIM model.
When exporting a model to IFC you almost always face the same question: IFC 2x3 or IFC 4? Both are schemas of buildingSMART's open IFC standard (Industry Foundation Classes), but they have differences that matter when auditing the model and delivering it to a client.
What the IFC schema is (and why there are versions)
IFC is the open, neutral format for exchanging BIM information between different software (openBIM). Like any standard, it evolves: each "schema" (2x3, 4, 4.3...) defines which entities exist, which properties they can have and how geometry is represented. Choosing the right schema ensures information travels complete between platforms.
IFC 2x3: the established standard
Published in 2006, IFC 2x3 (formally IFC2x3 TC1) is still, today, the most supported and battle-tested schema in the industry. Its characteristics:
- Maximum compatibility: practically all BIM and coordination software reads it without problems.
- Stability: after years of use, exporters are very refined and behavior is predictable.
- Limitations: less efficient geometry, more rigid property definitions and less support for certain domains (for example MEP or infrastructure).
IFC 4 (IFC4): richer and more efficient
IFC 4 is the major evolution of the schema. It brings concrete improvements:
- More efficient geometry: new representations (for example optimized tessellated surfaces) that reduce file size and improve the fidelity of complex shapes.
- Better handling of properties and materials: richer, more standardized definitions, useful for extracting quantities and classifying elements.
- New entities: broader domain coverage and a more orderly structure.
- Alignment with ISO 16739: IFC4 is the basis of the current international standard.
The trade-off: software and workflow support has historically been a step behind 2x3, although today it is widely available.
Quick decision table
- Maximum compatibility with older viewers and coordination → IFC 2x3.
- Models with complex geometry and a need for rich data → IFC 4.
- The client specifies a schema in the BEP/EIR → use the one the contract requires, no exceptions.
- In doubt and with no contractual requirement → IFC 2x3 is still the safest bet for interoperability; IFC 4 if your software chain supports it well end to end.
The most important thing: consistency
Beyond the version, the most costly mistake is mixing schemas between disciplines of the same project or switching versions between deliverables. Define the schema in the BIM Execution Plan and keep it consistent across the whole cycle. The same model exported in 2x3 and in 4 can differ in how properties are named or elements are grouped, and that complicates review.
And for auditing compliance?
For the purpose of auditing standard compliance, what matters is that the model has correct naming, classification, properties and levels, regardless of the schema. A good audit tool must be able to read both IFC 2x3 and IFC 4 and evaluate the model with the same criteria.
Verify your model, whether it is 2x3 or IFC 4
BIMaudit audits IFC models (2x3 and IFC 4) against a public standard aligned with ISO 19650 and gives you a compliance traffic light per category, objectively and traceably. Upload your model and check in minutes whether it is ready to deliver, no matter the schema you chose.