IFC File Format Explained: What it is and How to Open It

The IFC file has marked a real turning point in the AEC industry, providing a shared, open standard that enables all stakeholders to communicate and collaborate effectively throughout the entire lifecycle of a project.

But what exactly is an IFC file? What is it used for? How is it structured, and how can it be viewed?

In this article, you’ll find clear answers to these questions, along with practical insights to help you understand how IFC can support your day-to-day work. You’ll also learn how to view and manage IFC files using a free online BIM viewer.

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What is an IFC file?

The IFC file is an open, non-proprietary file format, international standard ISO 16739, and can be used to exchange and share data during the design, construction, management, and maintenance phases among all parties and various applications developed by different software houses without the necessity for them to support native (proprietary) files.

However, IFC is not just an exchange format, but a schema, meaning an organized structure of data according to precise rules: the IFC schema can be thought of as a “storage system” for organizing and transporting digital data.

How to open IFC files directly from the browser.

IFC file format: explanation of formats and extensions

Although people commonly refer to “IFC file” in the singular, the standard by buildingSmart International includes several variations of the format to meet specific interoperability, storage, and data exchange needs. Understanding the difference between the extensions is not merely an academic exercise, but a practical necessity to optimize workflows and the management of informational content.

The official formats published on the site are:

• .ifc – this is the cornerstone of interoperability in the construction world. It is a format based on the STEP (ISO 10303-21) language, structured as a readable text file (ASCII).
  • Strengths – it is the most widespread format and supported by almost all authoring software (Revit, Archicad, Edificius, etc.). Its textual nature ensures maximum compatibility over time: even without specific BIM software, the data can be viewed through a simple text editor;
  • Typical use – it is the standard for delivering BIM models, multidisciplinary coordination, and long-term archiving.
• .ifc-xml – uses the XML (Extensible Markup Language) language to structure model data. Instead of following the STEP syntax, data is organized through hierarchical “tags,” making it a format particularly suited to the world of web development and integration with corporate databases.
  • Strengths – although file sizes tend to be significantly larger than the standard .ifc format, its readability by external (non-BIM) applications and ease of parsing make it ideal for data exchange with management systems (ERP) or data analytics platforms;
  • Typical use – advanced software integrations and automated workflows that require manipulation of XML strings.
• .ifc-zip – as the name suggests, a .ifczip file is nothing more than a compressed archive containing an IFC (or IFCXML) file. Since textual IFC files can become extremely large in major projects, compression becomes a logical step to facilitate sharing.
  • Strengths – the reduction in file size can reach up to 80-90% compared to the original file, making sending via email or uploading to the cloud much faster;
  • Typical use – rapid exchange of large models between professionals and uploading to collaboration platforms.
• .ttl – The .ttl format, better known as Turtle, represents the evolution of IFC towards the world of Linked Data and Semantic Web. It uses the ifcOWL ontology to transform geometric and alphanumeric data into a network of relationships (triples).
  • Strengths – it is an extremely concise encoding and much more readable to the human eye compared to XML. Its “subject-predicate-object” structure allows linking BIM model information to other external databases (such as weather data, IoT sensors, or online price lists) without duplicating files.
  • Typical use – advanced research projects, management of complex Digital Twins, and contexts where the BIM model needs to “communicate” in real-time with the web.
• .rdf – similar to the Turtle format, the .rdf extension (often expressed as RDF/XML) is another encoding based on the ifcOWL ontology. While Turtle emphasizes conciseness, RDF is the historical standard for describing resources in the semantic web.
  • Strengths – being a consolidated W3C standard, it enjoys native compatibility with a vast range of data analysis tools and logical inference engines. It is the ideal format for anyone wanting to query the BIM model not just as a simple geometric file, but as a global relational database.
  • Typical use – integration into Smart City ecosystems and management of large real estate assets where semantic interoperability is prioritized over pure 3D modeling.

If you want to know what the other BIM formats are, I recommend reading the article “BIM Files: the main BIM formats for design.”

Interoperability in a closed and open system

IFC Schema Versions: IFC2x3, IFC4 and Beyond

In the BIM landscape, the version of the IFC schema defines the “rules of the game”: it establishes which objects can be exchanged, which properties they can possess, and how these must be related to each other. It is not just about software updates, but about genuine evolutionary leaps in the digitalization of construction.

What is an IFC schema?

The IFC schema is the standardized dictionary and logical framework that defines how information should be structured within a file. Based on the EXPRESS data modeling language, it organizes data in a strict hierarchy (classes, attributes, and relationships). Without a shared schema, software would not be able to interpret whether a certain geometric solid represents a column, a beam, or a pipe, nor correctly read its thermal or structural properties.

IFC2x3: features and limitations

Released in 2003, the IFC2x3 version is still the most widely used globally due to its stability and software consolidation.

It introduced the concept of Model View Definition (MVD) to coordinate the exchange between architects and structural engineers (Coordination View), although it has gaps in managing complex geometries (curved surfaces), limited flexibility in defining custom property sets, and virtually no coverage regarding civil infrastructures.

IFC4: improvements and new features

Certified as the ISO 16739:2013 standard, the IFC4 version represents a fundamental leap in quality.

It introduced support for more efficient and complex geometries, improved documentation, and a reduction in data ambiguities. It includes new classes for energy efficiency and support for environmental design workflows. It was designed to be more “lightweight” and to facilitate integration with modern web technologies.

IFC4.3: infrastructures and advanced use cases

IFC4.3 is the current frontier of Open BIM, finally extending the standard to the world of infrastructures (BIM Infrastructure).

It includes specific definitions for roads, railways, bridges, ports, and waterways. In addition, it enables the management of the lifecycle of complex linear works, harmonizing the civil engineering sector with the building sector, which until a few years ago operated on separate technological tracks.

Representation of elements organized according to the IFC schema

When to Use Different Types of IFC Files in BIM Projects

The choice of IFC format and version should not be regarded as merely a technical decision or a software automatism, but rather a strategic choice that directly affects the fluidity of collaboration. Each phase of the lifecycle of a project indeed requires a specific level of detail and data structure: knowing how to select the correct file is the only way to avoid precious information loss during transitions between different professionals.

File Exchange Between BIM Authoring Software

In the early stages of design, the heart of the activity lies in the continuous exchange between different authoring software, for example, when the architectural model needs to be integrated with the structural model. In this context, the text-based .ifc standard format remains the preferred choice for its universality. However, the true difference is made by the version of the schema: if the work team has up-to-date software, the adoption of IFC4 is strongly recommended. This version indeed allows for the management of complex geometries and curved surfaces with millimeter precision, drastically reducing the graphical approximations often encountered during import into different environments.

Coordination and Clash Detection

When the project enters the heart of multidisciplinary coordination, the priority shifts to the ability to manage large amounts of data. Overlapping architectural, structural, and system models to identify spatial interferences makes file lightweightness critical. In these situations, the .ifczip format proves to be the most efficient tool, allowing the movement of complex federated models without saturating hardware resources. Many BIM coordinators still prefer to rely on the IFC2x3 schema at this stage, as its established stability ensures superior processing speed in model checking software and near-total compatibility with every validation tool available on the market.

From Model to Estimate: Quantitative Analysis and Cost Estimation

In the transition from the 3D model to budgeting, geometry gives way to alphanumeric data and quantities. Here, the IFCXML format can offer significant advantages, especially when the quantification software needs to communicate with external price databases or corporate management systems. The “tag” structure typical of XML facilitates massive data extraction, provided that the professional has correctly configured the Property Set (Pset) within the model. The ultimate goal is to transform every geometric entity into a certified cost item, effectively eliminating the human error typically associated with manual measurements on two-dimensional drawings.

The Future of Management: Facility Management and Digital Twin

With the completion of the construction site, the IFC model must evolve to become a dynamic database of the completed work, the so-called As-Built. At this advanced stage, the use of formats such as .ttl or .rdf opens revolutionary scenarios. Thanks to the ifcOWL ontology, the BIM model ceases to be a static file and becomes a node within a network of interconnected data. This allows for connecting every component of the building to IoT sensors, monitoring energy performance or the wear state of systems in real-time. Thus, we move from a simple informational model to a true Digital Twin, capable of communicating with the web and providing predictive maintenance information.

How to open an IFC file

To open an IFC file, you can follow two procedures:

• buy a BIM software that supports importing this format;
• use a free online BIM viewer.

Now I will explain how to do this using an online viewer. You do not need to download any application, just:

• create your personal account and log in to usBIM;
• import the IFC file you want to open into a folder;
• view the model in 3D, the entities, and the properties.

IFC file structure: what does an IFC file contain?

The IFC format allows the production of files that include:

• geometric information of various entities of “simple” building components (such as walls, doors, slabs, etc.) and all data associated with them;
• alphanumeric information (properties, quantities, classification, etc.) that specify their parameters, physical properties, construction information, maintenance information, etc.

The structure of an IFC file is based on 3 fundamental elements:

• IfcObjectDefinition: the entities (objects);
• IfcRelationship: the relationships between the entities;
• IfcPropertyDefinition: the properties associated with the entities.

IFC data schema composition diagram

A BIM model is a model made up of specific parametric entities that have relationships with each other and whose technical characteristics are described through properties. It is therefore natural that the pillars of the structure of the standard refer to these concepts.

To delve deeper into this subject, I recommend reading the following articles:

• IFC file architecture (part 1): IfcObjectDefinition;
• IFC file architecture (part 2): the concept of IfcRelationship;
• IFC file architecture (part 3): IfcPropertyDefinition.

Model View Definition and BIM

MVDs represent subsets of the IFC schema defined by buildingSMART International that group together certain information useful for specific workflows or uses.

These “filtered views” are very useful as they simplify the data exchange process and avoid the sharing of unnecessary or redundant information, following standardized procedures.

The following image shows a diagram that conveys the completeness of the IFC schema and how a specific MVD can streamline it according to the information useful for a particular purpose.

IFC schema and MVD variation

As can be seen from the previous image, the MVD is a filtered view that captures a part of the information from the entire schema or a portion of it.

Therefore, the function of the MVD does not depend on the many software available on the market, but on the information that one wants to share.

This is the result of a specific need, namely to transfer the necessary information for a particular situation, facilitating the exchange between software available internationally.

Read the article “Model View Definition (MVD) and BIM Data Exchange” and learn more about this topic.

Classification Systems in the Construction Sector

The classification system is a method of grouping and coding that makes it possible to organize entities.

There are different types of classifications, with various ways of dividing into categories.

Among these, we mention:

• Omniclass;
• Uniclass;
• Uniformat;
• Masterformat;
• etc.

To learn everything about classification systems in construction, I suggest the article “IFC and Classification Systems in the Construction Sector.”

Before concluding, here are two practical tips that address the most common needs of technicians: opening an IFC file and converting a DWG file to IFC.

IFC File: whitepaper to Download

Below, I propose a Whitepaper (technical document with all the main information) containing a collection of articles on the IFC topic, published on BibLus BIM.

To learn everything about IFC, download the ACCA whitepaper.

FAQ on what an IFC file is and how to open it

What is an IFC file?

An IFC file is an open, non-proprietary file format, an international standard ISO 16739, used to exchange and share data among all figures and applications during the design, construction, management, and maintenance phases. It is not just an exchange format, but a schema, meaning an organized structure of data according to specific rules, comparable to a ‘storage system’ for transporting digital data.

What are the main formats and extensions of the IFC file?

The official formats provided by the buildingSmart standard are: 1. .ifc: standard ASCII text-based format (ISO 10303-21), the most widely used for model delivery; 2. .ifc-xml: uses XML language, ideal for integration with business databases; 3. .ifc-zip: compressed archive that reduces file size by up to 80-90%; 4. .ttl: Turtle encoding based on ifcOWL for the world of Linked Data; 5. .rdf: W3C standard for resource description in the semantic web.

What are the differences between the versions of the IFC schema?

The main versions are: IFC2x3 (released in 2003, the most widespread for stability, introduces MVDs); IFC4 (ISO 16739:2013 standard, supports more complex geometries and environmental design flows); IFC4.3 (the current frontier of Open BIM which extends the standard to the world of infrastructure such as roads, railways, and bridges).

When is it advantageous to use the different types of IFC files?

The choice is strategic: for exchange between authoring software, the standard IFC is preferred (better IFC4 for curved geometries); for coordination and clash detection, .ifc-zip is often used for its lightweight; for quantity takeoff, IFCXML facilitates data extraction; for Facility Management and Digital Twins, .ttl or .rdf formats are recommended due to the ifcOWL ontology.

How to open an IFC file directly from the browser?

To open an IFC file without downloading applications, you can use a free online viewer like usBIM. Simply create a personal account, import the IFC file into a folder, and view the 3D model with its associated entities and properties directly on the web.

What does the structure of an IFC file contain?

An IFC file includes geometric information of building components and alphanumeric information (properties, quantities, classifications). It is based on 3 fundamental elements: IfcObjectDefinition (the entities), IfcRelationship (the relationships between the entities), and IfcPropertyDefinition (the associated properties).

What is a Model View Definition (MVD)?

MVDs are subsets of the IFC schema defined by buildingSMART that group certain information useful for specific workflows. They represent ‘filtered views’ that streamline the IFC schema to transfer only the information necessary for a given purpose, facilitating the exchange between software.