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

# API client requirements

Sendcloud takes your and your customers' security seriously. Therefore, before interacting with our API, please check if your client supports the protocols and security features we require.

## HTTPS (TLS)

A secure connection is enforced. Please always connect to the Sendcloud API using HTTPS. We only support TLSv1.2 and higher, as lower versions are no longer considered secure. This means that SSLv3 and SSLv2 are also not supported.

### Certificate

Our certificate is signed by Amazon Root CA. Most operating systems and clients have built-in support for automatically verifying these certificates. In case yours doesn't, you can add the [AWS CA](https://docs.aws.amazon.com/privateca/latest/userguide/PCACertInstall.html) to your list of trusted Certificate Authorities (CA). Note that our API's server certificate is rotated regularly and it is therefore not recommended to pin our certificate instead.

### Supported TLS Ciphers

A cipher suite is a set of algorithms that help secure a TLS connection.

The Sendcloud API supports the following ciphers:

* `TLS_AES_128_GCM_SHA256`
* `TLS_AES_256_GCM_SHA384`
* `TLS_CHACHA20_POLY1305_SHA256`
* `TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256`
* `TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384`
* `TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256`

## HTTP version

The Sendcloud API supports both `HTTP/1.1` and `HTTP/2`. `HTTP/3` is not (yet) supported. `HTTP/1.0` is not supported.

## `GET` requests that include a body

<Warning>
  The Sendcloud API does not support `GET` requests that include a body.

  If a `GET` request includes a body, the server will respond with HTTP status code `403 (Forbidden)`.
</Warning>

## IP version

Currently our API is only available using IPv4.