> ## Documentation Index
> Fetch the complete documentation index at: https://docs.activecalculator.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Introduction

> Fundamental concepts of ActiveCalculator's API.

<Info>
  ActiveCalculator's API is now available for use. Integrate powerful calculation capabilities into your applications.
</Info>

## Base URL

ActiveCalculator's API is built on REST principles and is served over HTTPS. To ensure data privacy, unencrypted HTTP is not supported.

The Base URL for all API endpoints is:

```bash Terminal theme={null}
https://app.activecalculator.com/api/v1
```

## Authentication

Authentication to ActiveCalculator's API is performed via the `x-ac-api-key` header. To authenticate, you need to include this header with your API key in your requests like so:

```bash Terminal theme={null}
x-ac-api-key: <Your-API-Key>
```

Learn more about [how to get your API key](https://activecalculator.com/help/article/api-keys).

## Response Codes

The API returns standard HTTP response codes to indicate the success or failure of an API request. Here are a few examples:

| HTTP Code | Error Code              | Description                                           |
| --------- | ----------------------- | ----------------------------------------------------- |
| 200       | -                       | The request was successful.                           |
| 400       | `bad_request`           | The request was invalid or cannot be served.          |
| 401       | `not_authenticated`     | The request lacks valid authentication credentials.   |
| 401       | `unauthorized`          | The request is not authorized to access the resource. |
| 404       | `not_found`             | The requested resource could not be found.            |
| 405       | `method_not_allowed`    | The HTTP method is not supported for this endpoint.   |
| 500       | `internal_server_error` | The server encountered an unexpected condition.       |