# What “OpenAI-compatible” means

> An OpenAI-compatible API accepts the same request and response format as OpenAI's Chat Completions API. Any OpenAI SDK or tool can use it by changing the base URL and the API key, which is how one gateway can offer models from many companies behind one familiar interface.

Source: https://digitspace.ai/learn/openai-compatible-api · Last checked: 2026-10-30

## What to check for

| Feature | Why it matters |
| --- | --- |
| Streaming (server-sent events) | Chat interfaces and agents show text as it arrives |
| Tools (function calling) | Agents and structured actions depend on it |
| JSON schema output | Reliable structured data |
| Images in messages | Vision features |
| Usage in the response | Token counts for cost tracking |

## And Anthropic-compatible

Anthropic's Messages API is the other common format, used by Claude Code and Anthropic's SDKs. DigitSpace accepts both, and translates between them, so a GPT model can be called through the Messages API and a Claude model through Chat Completions.

## Questions

### Do all models behave the same through it?

The format is the same; what each model supports differs. A router that knows each model's capabilities sends requests only where they'll work.

### Is OpenAI's Responses API the same thing?

No, it's a newer, different format. DigitSpace serves Chat Completions and Messages today.

## Related

- [API compatibility](https://digitspace.ai/features/api-compatibility)
- [Coding agents](https://digitspace.ai/solutions/coding-agents)
- [Docs](https://digitspace.ai/docs)
- [What is an AI gateway?](https://digitspace.ai/learn/what-is-an-ai-gateway)

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