OpenRouter Documentation

Complete reference for the OpenRouter API platform. All documentation is stored in references/.

Quick Navigation

Consult references/INDEX.md for the full table of contents with descriptions of every page.

When to Read Which Files

• Getting started: Read references/quickstart.md
• API basics (endpoints, auth, params, errors): Read files in references/api/reference/
• Chat completions: Read references/api/api-reference/chat/send-chat-completion-request.md
• Streaming: Read references/api/reference/streaming.md
• Model selection & routing: Read files in references/guides/routing/
• Model variants (:free, :nitro, etc.): Read files in references/guides/routing/model-variants/
• Tool calling / function calling: Read references/guides/features/tool-calling.md
• Structured outputs (JSON schema): Read references/guides/features/structured-outputs.md
• Embeddings: Read references/api/reference/embeddings.md
• Authentication & OAuth: Read files in references/guides/overview/auth/
• SDK usage (TypeScript): Read files in references/sdks/typescript/
• SDK usage (Python): Read files in references/sdks/python/
• Framework integrations (Vercel AI, LangChain, etc.): Read files in references/guides/community/
• Observability (Langfuse, Datadog, etc.): Read files in references/guides/features/broadcast/
• Multimodal (images, audio, video, PDF): Read files in references/guides/overview/multimodal/
• Guardrails & spending controls: Read references/guides/features/guardrails.md
• Pricing & credits: Read references/api/api-reference/credits/
• Error handling: Read references/api/reference/errors-and-debugging.md
• Rate limits: Read references/api/reference/limits.md
• Best practices (latency, caching, uptime): Read files in references/guides/best-practices/
• Enterprise setup: Read references/enterprise-quickstart.md
• Responses API (beta): Read files in references/api/reference/responses/

Key Concepts

• Base URL: https://openrouter.ai/api/v1 (OpenAI-compatible)
• Auth header: Authorization: Bearer <OPENROUTER_API_KEY>
• Model format: provider/model-name (e.g. openai/gpt-4o, anthropic/claude-sonnet-4-5)
• Variants: Append :free, :extended, :nitro, :thinking, :online to model IDs
• Fallbacks: Pass array of models to models field for automatic fallback
• Provider routing: Use provider.order, provider.only, provider.ignore for control