1. Introduction

In the OpenAI ecosystem, developers can interact with models through two main APIs: the Responses API and the Chat Completions API. This tutorial will explore the differences between these two, their applicable scenarios, and how to choose the API that best suits your project needs.

2. Overview Comparison

Responses API · Positioning: The latest core API, a proxy-type API primitive · Features: Combines the simplicity of Chat Completions with capabilities for more agentic tasks · Recommended for: New users · Built-in tools: Web search, file search, computer use

Chat Completions API · Positioning: Industry standard for building AI applications · Features: Stable, widely used · Future plans: OpenAI plans to support it indefinitely

When to Use the Responses API

The Responses API is our latest core API and a proxy API primitive that combines the simplicity of chat completions with the ability to perform more agentic tasks. As model capabilities continue to evolve, the Responses API will serve as a flexible foundation for building action-oriented applications, with the following built-in tools: