> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://developers.brevo.com/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://developers.brevo.com/_mcp/server.

## Where do I sign up to use the API?

Create a free account on [Brevo.com](https://app.sendinblue.com/account/register). After signing up, access the [API Console](https://account.sendinblue.com/advanced/api) to manage your API keys.

## Where do I get the API keys?

Manage your API keys from the [API Console](https://account.sendinblue.com/advanced/api). Use the latest version — v3 access keys.

Create a new API v3 key from your [API Console](https://account.sendinblue.com/advanced/api). To generate an API v3 key directly from your code, use the API v2 endpoint that creates and returns one.

```curl cURL
curl -H 'api-key:yourApiV2Key' -X POST -d '{"name":"My v3 key name"}' 'https://api.brevo.com/v2.0/account/generateapiv3key'
```

## Is my programming language supported?

Brevo is language-agnostic and supports any language that can make HTTP calls. We also provide [clients](/docs/api-clients) for the most commonly used languages.

## Some API calls that I need are missing?

We aim to cover as much of the platform in our APIs as possible. If a feature is missing, [contact us](https://www.sendinblue.com/contact/).

## How do I keep up with the changes to the Brevo API?

Changes and updates to the API are listed in [Version Upgrades](/changelog).

## How can I be sure my data is being securely transmitted to Brevo?

The API runs over HTTPS, so data exchanged between you and Brevo cannot be read or intercepted. Communication requires a unique API key, which you can rotate periodically.

## What output formats are supported by the API?

The Brevo API returns JSON. See [details here](/docs/how-it-works#responses).

## Are there circumstances which would terminate my access to the API?

Misuse of our systems is not allowed. Your account will be terminated if usage does not comply with our terms of use. See our [terms and conditions](https://www.sendinblue.com/legal/generalterms/) for details.

## What if I have additional questions?

Contact [support](https://www.sendinblue.com/contact/) for any questions about using the Brevo API.

## Where can I view sample code?

The API Reference includes examples for every endpoint. Sample code is available in PHP, Java, C#, Node.js, Python, and Ruby.

## What if there are errors in the documentation?

We keep the documentation accurate and up to date. If you find an error, [contact us](https://www.sendinblue.com/contact/) and we'll fix it.

## How can I test the API?

Test the API directly in the reference section. Enter your API key and parameters.

> ❗️
>
> It's **not a sandbox**. All calls are reflected in your account, and credits are deducted for billing events (for example, email sending).

## In which all cases can I send custom headers with the transactional email?

**Route:** [/reference/send-transac-email](/reference/send-transac-email)

* **Case 1:**      *htmlContent* allows custom headers
* **Case 2:**     *textContent* allows custom headers
* **Case 3.1:**   *attachment url* allows custom headers
* **Case 3.2:**  *attachment* in base64 allows custom headers
* **Case 4:**     *templateId* allows custom header with New Templating Language

**NOTE:** Custom headers are not allowed when sending *templateId* with *Old Templating Language*.