What is a CAD API?
A CAD API (application programming interface) is the set of classes and functions a CAD vendor exposes so that developers can read, create and modify models, drawings and data from code. With it you can automate tasks, add commands, validate designs and connect CAD to other systems.
The major CAD APIs
| Platform | Main APIs | Languages |
|---|---|---|
| AutoCAD & verticals | AutoLISP, .NET API, ObjectARX, JavaScript | LISP, C#, VB.NET, C++ |
| Autodesk Inventor | Inventor API, iLogic | C#, VB.NET, iLogic (VB) |
| Autodesk Revit | Revit API, Dynamo | C#, Python (pyRevit / Dynamo) |
| Autodesk Fusion | Fusion API, post processor engine | Python, C++, JavaScript (posts) |
| SOLIDWORKS | SOLIDWORKS API, PDM API, Document Manager | C#, VB.NET, VBA, C++ |
| PTC Creo | Creo TOOLKIT, J-Link / Object TOOLKIT, Web.Link | C, C++, Java, JavaScript |
| CATIA V5 / 3DEXPERIENCE | CAA C++, Automation (COM), EKL | C++, VBA, VB.NET, C# |
| Siemens NX | NX Open, Knowledge Fusion | C#, C++, Python, Java |
Types of CAD API projects
- In-process add-ins that run inside the CAD application with custom commands and UI.
- Standalone automation applications that drive CAD in the background, for example batch exports.
- Headless or cloud processing using services like Autodesk Platform Services (APS) Design Automation.
- Integrations that sync CAD data with ERP, PLM, PDM, CRM or databases.
- Configurators that generate models and drawings from rules and inputs.
A sensible architecture
Keep CAD-specific code thin and put your business rules in a separate, testable layer. That way the same rules can serve an AutoCAD add-in today and a SolidWorks or web tool tomorrow.
UI layer ribbon buttons, dialogs, palettes
CAD adapter calls the CAD API (AutoCAD, SolidWorks, Creo ...)
Business rules your design logic, validation, numbering
Data layer Excel, SQL database, ERP / PLM APIsThe development process
- Discovery: map the current workflow and collect sample files.
- Specification: define inputs, rules, outputs and CAD versions to support.
- Prototype: prove the hardest part of the API first.
- Build and test: with real models, edge cases and users.
- Deploy: installers, licensing and version management.
- Maintain: rebuild and test for each yearly CAD release.
Common pitfalls
- Ignoring CAD version differences. APIs change and some releases require new .NET versions.
- Hard-coding paths, templates and standards instead of using configuration.
- No error handling, leading to crashes or half-finished models.
- Building everything at once instead of delivering value in stages.
The API is the easy part. Understanding the engineering workflow is what makes a CAD tool successful.
Choosing a CAD API partner
Look for experience across several CAD platforms, real engineering understanding, clean code you own, and a plan for long-term maintenance. ENGIMANDI is an official Autodesk Development Partner and delivers AutoCAD API development and multi-CAD customisation for clients worldwide.