What GPC is
Global Privacy Control is a browser-level signal through which a visitor says, in a standardized way, do not sell or share my personal data. It travels as an HTTP header and a JavaScript property, set by the browser or an extension, and it applies across every site the visitor opens. Unlike a cookie banner choice, which is per-site and per-session, GPC is a standing preference the visitor sets once and expects every site to respect.
The key concept is that GPC is the visitor speaking, not the site asking. The banner is your interface for requesting consent. GPC is the visitor's interface for refusing sale and sharing. Both exist in the same visit, they govern overlapping but distinct things, and your implementation has to handle both without making them fight.
Where it has legal weight
GPC is not a nice-to-have privacy feature. In California, regulations under the CCPA treat a GPC signal as a valid opt-out request that businesses must honor. Colorado's privacy law similarly recognizes universal opt-out mechanisms. Enforcement attention has followed: regulators have pointed to GPC handling in actions and guidance, and the signal keeps appearing in the compliance checklists that auditors use.
The practical consequence is that ignoring GPC is now a documented compliance gap, not a gray area. If your site sells or shares personal data as those laws define it, which includes common advertising and analytics sharing arrangements, a GPC signal from a covered visitor is an opt-out you must effectuate. The banner does not substitute for it. A visitor can ignore your banner entirely and still have opted out through GPC.
How to honor it
Implementation has two parts: detection and effectuation. Detect the signal server-side from the request header or client-side from the JavaScript property, and do it on every page load, not just the landing page. Then treat it as an opt-out of sale and sharing: suppress the tags, pixels, and data transfers that constitute sale or sharing under the applicable law, for that visitor, for the session.
The suppression has to be real. Detecting the signal and logging it while the advertising tags fire anyway is worse than not detecting it at all, because the log proves you knew. Map your tag inventory to sale and sharing categories in advance, so the GPC handler knows exactly which tags to hold. Test with a GPC-enabled browser and confirm in the network log that the suppressed tags actually stay silent.
GPC and your banner together
The banner and GPC govern different scopes and they should not be merged into one control. The banner handles granular consent for cookies and processing purposes. GPC handles the universal opt-out of sale and sharing. A visitor who sends GPC and then accepts everything in your banner has given mixed signals, and the safe interpretation is that the opt-out stands for sale and sharing regardless of banner interaction.
Show GPC status in the preference center so the visitor can see it was received. Do not require GPC visitors to complete the banner to effectuate the opt-out; the signal is already the choice. And keep the two systems' records separate but linked: the consent record shows banner choices, the GPC log shows signal receipt and the suppression actions taken. When a regulator asks, you want both stories clean and consistent.
Testing and documentation
Test quarterly with a fresh profile and a GPC-enabled browser. Load the site, confirm the signal is detected, and verify in the network log that sale and sharing tags do not fire. Then interact with the banner, accept everything, and verify the GPC suppression still holds for the tags it covers. Document the test: date, browser, what was checked, what was found.
Update the privacy policy to describe GPC handling in plain language: what the signal means, what you do when you receive it, and how it interacts with banner choices. The policy is where regulators look first, and a site that detects GPC, honors it, tests it, and documents it is a site that has nothing to fear from the question. The sites that should worry are the ones that have never checked.
Frequently asked questions
What is Global Privacy Control?
GPC is a browser or extension signal a visitor can send to tell sites they do not want their personal information sold or shared, or that they are opting out of targeted advertising, depending on the regime. It arrives automatically with every request where it is enabled.
Must sites honor the GPC signal?
In several jurisdictions, yes, for the purposes the signal covers, and the list grows. Sites should detect the signal, apply it to the relevant processing, and record that they did, rather than treating it as optional metadata.
How does GPC interact with a consent banner?
GPC acts as a standing opt out for its covered purposes. If a visitor with GPC active later makes banner choices, the interaction between the two needs a defined rule in your consent setup, applied consistently and documented.