Azure OpenAI Service vs OpenAI API, which to use and when in 2026

When someone asks whether to use Azure OpenAI Service or the direct OpenAI API, the starting point is this: the models running on both platforms are identical. GPT-4o, GPT-5, and the o-series models you deploy on Azure have the same weights, the same capabilities, and the same output quality as the ones you call from platform.openai.com, and what changes between the two platforms is the infrastructure where they run, the authentication mechanism, and the compliance guarantees the provider can offer on those requests. What changed in 2026 Azure AI Foundry was renamed Microsoft Foundry on January 1, 2026, and Azure OpenAI Service now lives inside that unified platform alongside the model catalog, development tooling, and agents. References to Microsoft Foundry in new documentation point to what used to be Azure AI Foundry. In July 2026, the GPT-5.6 family arrived with Sol, Terra, and Luna available on Azure the same day as on the direct OpenAI API. Historically Azure lagged four to eight weeks behind new model releases because Microsoft validates them within their compliance frameworks before making them available, and while that gap still exists for some specific features and APIs, for the main models in the GPT-5 family availability is converging. Where data is processed When you call GPT-4o from the OpenAI API, the request goes to OpenAI's own infrastructure, which is centralized and gives you no control over which region processes your data. For most use cases that doesn't matter, but for organizations with data residency requirements, regulatory compliance needs, or industries like healthcare, banking, or government, that detail can determine whether the service is usable at all. Azure OpenAI runs the same models within the boundary of your Azure tenant, so the data you send in prompts doesn't leave to OpenAI's infrastructure but processes in the Azure regions you choose. That's what makes it possible to meet HIPAA, SOC 2, EU data residency, and other certificati