# What is IFC?

IFC, the Industry Foundation Classes, is an open standard from buildingSMART for describing a building and everything in it as data, so that different programs can exchange a model. An IFC file holds elements, their properties and their places in the building. IFC Checker reads IFC files in the STEP format in the versions IFC2X3, IFC4 and IFC4.3.

Updated 1 November 2026

## What an IFC file holds

An IFC file describes a building as a list of records. A record can be an element, such as a wall, a door or a space, a property set that an element carries, a material, a classification, or a relationship, for example that a door is in a wall, or that a wall is on a storey. Elements have a class, such as `IfcWall`, and an identity, a GlobalId, which a tool should keep the same from one export to the next. A model can also carry the shapes of its elements, which IFC Checker draws in the 3D view, but a check reads the information.

The file is plain text in the STEP format. It starts with a header that names the schema it is written in, and has a DATA section of numbered records. [Model health](https://ifcchecker.com/help/model-health/) checks that every record can be read and that the file matches its schema.

## IFC and IDS

IFC says what a model contains. [IDS](https://ifcchecker.com/help/what-is-ids/) says what a model must contain. IFC Checker reads the first and tests it against the second.

## Try it in IFC Checker

1. Add an IFC model on **Check**. The row of the model says which IFC schema its header names.
2. After the check, find the schema again in the **Schema** column of the **Model** table.

## Where the schemas are documented

buildingSMART publishes every release with its documentation. The page that lists them all is [buildingSMART: IFC schema specifications](https://technical.buildingsmart.org/standards/ifc/ifc-schema-specifications/). The three releases IFC Checker reads:

- [IFC 4.3 documentation](https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/), the release IFC Checker calls IFC4X3_ADD2, for buildings and infrastructure
- [IFC4 documentation](https://standards.buildingsmart.org/IFC/RELEASE/IFC4/ADD2_TC1/HTML/), Addendum 2, Technical Corrigendum 1
- [IFC2X3 documentation](https://standards.buildingsmart.org/IFC/RELEASE/IFC2x3/TC1/HTML/), Technical Corrigendum 1, the older release that many tools still export

- [buildingSMART: Industry Foundation Classes (IFC)](https://technical.buildingsmart.org/standards/ifc/), the standard and its releases

[Which versions IFC Checker reads, and how](https://ifcchecker.com/help/ifc-versions/).

## Keep reading

Next: [What is IDS?](https://ifcchecker.com/help/what-is-ids/)

Related:

- [What are BIM and openBIM?](https://ifcchecker.com/help/what-is-openbim/)
- [What is IDS?](https://ifcchecker.com/help/what-is-ids/)
- [Which IFC and IDS versions are read?](https://ifcchecker.com/help/ifc-versions/)

[Workflows and help](https://ifcchecker.com/help/) / [Help](https://ifcchecker.com/help/collections/standards/)