OpenRouter OpenAI Compatibility

Overview

OpenRouter implements the OpenAI Chat Completions API specification (/v1/chat/completions). Existing OpenAI SDK code works with OpenRouter by changing two values: base_url and api_key. This gives you access to 400+ models from all providers through the same SDK interface.

The Two-Line Migration

Python (Before)

from openai import OpenAI

client = OpenAI(api_key=os.environ["OPENAI_API_KEY"])  # OpenAI direct
response = client.chat.completions.create(
    model="gpt-4o",
    messages=[{"role": "user", "content": "Hello"}],
)