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

# IP Versions

> Residential Proxy Internet Protocol Version Specification

<Warning>
  The IP version specification feature can be enabled with an active Residential plan. To request access to this feature, contact us at [support@decodo.com](mailto:support@decodo.com).
</Warning>

## IPv4/IPv6 Proxies

By default, the residential proxy pool has **both** IPv4 and IPv6 addresses.

To specify the Internet Protocol version with the residential proxy, you have to include the `ipv` variable in the proxy **username** or a **whitelisted IP**. The IP version is specified after the variable, like so: `ipv-4` & `ipv-6`.

If the target website supports only one of the IP versions, the proxy will **try to automatically resolve** the supported version. However, there is a possibility of the request failing, in which case you can try **specifying** the correct IP version or **retrying** the proxy request.

For example, if you are using an IPv6 proxy to target an IPv4-only website, the proxy will try to automatically resolve the website using an IPv4 proxy, and vice versa.

## Examples

### Username:password

**IP version specification** when the proxy authentication occurs via the **username** and **password** method.

* An example of a proxy that returns IP addresses from the **IPv4** proxy pool:

<CodeGroup>
  ```shellscript cURL theme={null}
  curl -U "user-username-ipv-4:password" -x "gate.decodo.com:7000" "https://ip.decodo.com/json"
  ```
</CodeGroup>

* An example of a proxy that returns IP addresses from the **IPv6** proxy pool:

<CodeGroup>
  ```shellscript cURL theme={null}
  curl -U "user-username-ipv-6:password" -x "gate.decodo.com:7000" "https://ip.decodo.com/json"
  ```
</CodeGroup>

### Whitelisted IP

**IP version specification** when the proxy authentication occurs via the **whitelisted IP** method.

* An example of a proxy that returns IP addresses from the **IPv4** proxy pool:

<CodeGroup>
  ```shellscript cURL theme={null}
  curl -x "https://ipv-4.gate.decodo.com:7000" "https://ip.decodo.com/json"
  ```
</CodeGroup>

* An example of a proxy that returns IP addresses from the **IPv6** proxy pool:

<CodeGroup>
  ```shellscript cURL theme={null}
  curl -x "https://ipv-6.gate.decodo.com:7000" "https://ip.decodo.com/json"
  ```
</CodeGroup>

<Note>
  ### Note

  The IP availability may be limited if targeting smaller countries or cities together with the `ipv` variable.
</Note>

***

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