Consent Mode decoder

How to read gcs

gcs is G1 followed by one character for ad_storage and one for analytics_storage: 1 granted, 0 denied. It says what the tag knew at the moment the request left.

How to read gcd

gcd looks like 11r1r1r1r5: a two-digit start, then one letter each for ad_storage, analytics_storage, ad_user_data and ad_personalization, separated by digits, and a closing digit. The separators and the ends vary; the four letters are what carry the meaning, and each says both the state and how it was reached.

What the decoder flags

• v2 incomplete — ad_user_data or ad_personalization is l, never set.
• An update with no default — m or n: the first requests left before any consent state existed.
• Granted before the visitor answered — t, v or u: the default was granted.
• gcs and gcd disagree — two tags on the page reading different states.

To see which vendors kept sending after consent was denied — the part Consent Mode itself does not cover — read Debugging Consent Mode V2.

Questions

What is the gcs parameter?

gcs travels on Google requests and gives the state of ad_storage and analytics_storage at the moment of the hit: G1 followed by one digit for each, 1 for granted and 0 for denied. G100 is both denied, G111 both granted.

What is the gcd parameter?

gcd carries all four Consent Mode v2 signals — ad_storage, analytics_storage, ad_user_data and ad_personalization — as letters, and each letter also says how the state came about: from the default, from an update, or both.

Is gcd documented by Google?

Not formally. The reading used here is the one published by Simo Ahava and widely used since; the Tag Master extension reads it the same way and treats letters it does not recognise as unknown rather than guessing.

Where do I find gcs and gcd?

In the request itself: open DevTools, Network, filter on collect, and read the query string of a GA4 or Google Ads request. Or paste the whole request URL here — the decoder pulls both out.

Does this page send what I paste anywhere?

No. It is read in your browser. The page address keeps only the gcs and gcd values, so a shared link never carries the rest of a request URL.