# GPC Step 01:

# Detect & record the GPC signal

In order to support the GPC, you'll need to understand how to detect the signal, appropriately record it, and process it.

## How to detect and manage the GPC

Detecting the Global Privacy Control from Javascript properties is quite straightforward. The globalPrivacyControl property enables any client-side javascript to confirm the user's current settings for the Sec-GPC field value.

The standard WebIDL that GPC provides for this is:

```
    interface mixin GlobalPrivacyControl {
      readonly attribute boolean globalPrivacyControl;
    };
    Navigator includes GlobalPrivacyControl;
    WorkerNavigator includes GlobalPrivacyControl;
```

The value of this is `false` if no `Sec-GPC` header field is sent, otherwise the value will be `true`.

From this, checking the user's current state is a case of checking GPC via a script such as the example below:

```
    if (!navigator.globalPrivacyControl) {
      // wonderful, we can share or process the users data
    }
```

## Format of the standard GPC header message

The Sec-GPC header field should only be created and set by the browser when the users Global Privacy Control preference is set to `true`. In this case, where the user’s preference is true, the Sec-GPC header field will be set to `1`, analogous to `true`.

As such, a valid HTTP request passing the Global Privacy Control will look something like:

```
    GET /something/here HTTP/2
    Host: example.com
    Sec-GPC: 1
```

## How to show your website supports the GPC

While it’s not mandatory, the best practices provided by the Global Privacy Protocol recommend that your site provide a .well-known URL to represent that you abide by the GPC.

In practice this means that to validate that you abide by the GPC, you would provide a JSON object located at the location:

```
    /.well-known/gpc.json
```

The contents of this JSON simply states whether you respect the GPC as `true` or `false` and the timestamp for when this resource was last updated.

An example of this provided by the GPC will look like this:

```
    Content-Type: application/json

{
      "gpc": true,
      "lastUpdate": "1997-03-10"
    }
```

If you're unsure how to setup GPC support you can ask the [Fides Slack Community (opens in a new tab)](https://fid.es/join-slack), or get [Privacy Engineering Intelligence from Ethyca (opens in a new tab)](/content/speak-with-us?utm_source=docs-site/index.html) now.