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OpenAPI.NET Delivers Its 'Biggest Update Ever' With Twin v2 and v3 Releases
Microsoft on Nov. 13 announced what it is calling the biggest update ever to its OpenAPI.NET library, releasing new v2 and v3 versions that expand specification support and improve the stability of API description handling.
The company said the pair of releases marks the most significant change to the project since it debuted in 2018, with updates aimed at keeping .NET API tooling aligned with the newest OpenAPI standards.
OpenAPI.NET is Microsoft's .NET library for reading, writing, and programmatically manipulating OpenAPI descriptions in JSON and YAML. It provides an object model used throughout the .NET ecosystem, supporting API-first workflows, code generation, validation, and integration with tools such as Swashbuckle, NSwag, and Semantic Kernel.
The new v2 release introduces support for the OpenAPI 3.1.0 specification. According to Microsoft's announcement, the update improves JSON parsing performance, simplifies dependency requirements by allowing JSON handling without additional packages, and adopts lazy reference resolution to make document loading more efficient. These changes are designed to reduce processing overhead while maintaining compatibility with YAML-based definitions.
The v3 release extends the library to support the OpenAPI 3.2.0 specification and updates a wide range of features across the object model. Microsoft notes enhancements in areas such as media type handling, schema and encoding properties, hierarchical tags with richer metadata, security flows and flags, expanded example capabilities, and broader parameter options. Together, the changes modernize the SDK's support for the newest version of the OpenAPI standard and increase what developers can represent in their API contracts. Microsoft's announcement characterizes the combined update as "the most significant update since its launch in 2018."
Microsoft encourages developers to review the upgrade guidance and update their NuGet packages to take advantage of the new capabilities. The releases are intended to support both current development practices and future .NET API tooling that depends on accurate, up-to-date OpenAPI definitions.
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David Ramel is an editor and writer at Converge 360.