ASP.NET Web API
ASP.NET Web API is a Microsoft framework designed to build HTTP-based APIs—interfaces that other applications can call to exchange data. Instead of rendering HTML pages for people, Web API returns structured data (for example JSON) for apps, websites, or mobile clients to consume. It was widely adopted by enterprises moving toward service-oriented and microservice architectures in the 2010s. Web API encouraged clear resource-based endpoints (e.g., "/customers/123") and worked hand-in-hand with security standards, versioning strategies, and documentation tools. It ran on the Windows-only .NET Framework, often alongside ASP.NET MVC for the human-facing parts of a site. Many corporate systems still rely on it today to connect front-end apps, mobile apps, and partner integrations.
Official WebsiteMigration Guidance
The modern successor is ASP.NET Core minimal APIs and controllers on .NET 6/8. Migrating unlocks much higher performance, cross-platform hosting, and the latest security and observability features. Remaining on legacy Web API increases technical debt and can make recruiting harder. A staged approach—standing up new endpoints in ASP.NET Core while keeping legacy ones running—lets you modernise safely without a "big bang" rewrite.
When to use ASP.NET Web API
Use ASP.NET Web API when supporting or extending existing systems that already expose endpoints with it. It remains a dependable choice for stable, intranet-style integrations or for incremental enhancements where a wholesale platform shift isn't yet practical.
Why choose ASP.NET Web API?
Teams chose Web API for its simplicity, strong tooling, and close alignment with the rest of the Microsoft stack. It made designing, testing, and documenting APIs approachable, and it integrated well with authentication, logging, and monitoring solutions familiar to .NET teams.