"Global Privacy Control (GPC) is a proposed specification designed to allow Internet users to notify businesses of their privacy preferences, such as whether or not they want their personal information to be sold or shared. It consists of a setting or extension in the user’s browser or mobile device and acts as a mechanism that websites can use to indicate they support the specification." -- Source : https://globalprivacycontrol.org/
GPC is inbuilt with Brave and DuckDuckGo browser, and from version 95.0 on-wards, Mozilla Firefox also began to support it. However, it is not enabled by default as of now. To enable GCP, follow the following steps.
Access about:config from your firefox browser, Search for globalprivacycontrol, and enable the two options to true.
To verify, go to https://globalprivacycontrol.org/ and if configured correctly, it will show the status.