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01: Detect & record GPC signals

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
    Sec-GPC: 1

How to show your website supports the GPC

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

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


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), or get Privacy Engineering Intelligence from Ethyca (opens in a new tab) now.