> For the complete documentation index, see [llms.txt](https://docs.nebulablock.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.nebulablock.com/api-reference/api-reference.md).

# Overview

Reference for Nebula Block's two APIs — the OpenAI-compatible Inference API and the Platform API.

Nebula Block exposes two APIs. They share one credential, so a single API key works against both.

| API                                                  | Base URL                               | Use it for                                                                 |
| ---------------------------------------------------- | -------------------------------------- | -------------------------------------------------------------------------- |
| [**Inference API**](/api-reference/inference-api.md) | `https://inference.nebulablock.com/v1` | Running models: chat, vision, images, video, embeddings, reranking         |
| [**Platform API**](/api-reference/platform-api.md)   | `https://api.nebulablock.com/api/v1`   | Managing resources: instances, SSH keys, API keys, object storage, billing |

The Inference API implements the OpenAI API surface, so existing OpenAI SDKs work against it by changing the base URL. The Platform API is a conventional REST API that wraps every response in a `data` / `message` / `status` envelope.

## Authenticating

Both APIs use Bearer authentication:

```
Authorization: Bearer sk-...
```

Create a key in the console under [API Keys](https://console.nebulablock.com/apiKeys). See [Authentication](/api-reference/authentication.md) for access tokens, login, and the rules around key rotation.

## Rate limits

Inference calls are subject to per-minute and per-day limits that depend on your tier, plus a per-model daily cap. Exceeding either returns `429`. See [Tiers and Rate Limits](/account/tiers-and-limits.md).

## Before you provision compute

Renting GPU instances requires an SSH key on your account, so that you can reach the instance once it is running. Add one in the console under [SSH Keys](https://console.nebulablock.com/sshKey), or with [Create SSH Key](/api-reference/platform-api/list-ssh-keys/create-ssh-key.md).

## See also

* [Quickstart](/getting-started/get-started/quickstart.md)
* [Model Catalog](/products/serverless-inference/model-catalog.md)
* [Glossary](/resources/glossary.md)