FBC and Cookie Data in general – differences GA4 Tag and Data Tag

Google Tag Manager Server Container
1

Hi,

I have set up sGTM and Facebook CAPI using your Tag and GA4 Client. Facebook tells me only 1% of purchases have fbc values.

In your code I can see that you take fbc from common_cookie

  • is common_cookie Data available with GA4 Tag / Client or only with Data Tag / Client?
  • What kind of non-google cookie data is GA4 Tag / Client sending to the server? (if any)
  • If I have only 1% of fbc coverage, could there be a problem with my GA4 Tag / Client setup and I better switch to Data Tag / Client?

Example code from FB CAPI Tag by stape:

const commonCookie = eventData.common_cookie || {};

let fbc = getCookieValues('_fbc')[0] || commonCookie._fbc;
let fbp = getCookieValues('_fbp')[0] || commonCookie._fbp;

if (!fbc) fbc = eventData._fbc;
if (!fbp) fbp = eventData._fbp;

Regards

2

Well, people have to click on your ad for clickid.. mabye thats the reason its low? becuase not a lot of people are acutally clicking your ad

3

Hi @DigitalMasters.

Just checking if I got this right. You are using Stape Data Tag + GA4 Client (default), correct? “[…] sGTM and Facebook CAPI using your Tag and GA4 Client […]”.
If so, I wouldn’t recommend this setup, as the GA4 Client (default) is to be used with the GA4 Tag. In its place, use the Stape Data Client GitHub - stape-io/data-client: Data Client for Google Tag Manager Server Side.

  • is common_cookie Data available with GA4 Tag / Client or only with Data Tag / Client?

common_cookie is available only for Stape Data Tag + Stape Data Client. They are sent inside the common_cookie parameter in the Stape Data Tag. And they are a fallback if the values are not found in cookies.
For the GA4 Tag / GA4 Client (default), only the cookies can be used as a source for the parameter.

  • What kind of non-google cookie data is GA4 Tag / Client sending to the server? (if any)

GA4 Tag / GA4 Client (default) doesn’t send any parameter with this information explicitly. You have either to pass it yourself manually, or read from the URL (page_location) or read from the cookies that are set on the user browser and can be accessed through sGTM.

  • If I have only 1% of fbc coverage, could there be a problem with my GA4 Tag / Client setup and I better switch to Data Tag / Client?

The fbc parameter is populated by the value of the fbclid URL parameter, which gets appended to the URL of your website (which in turn is saved into the cookie fbc) whenever someone comes from Meta’s platforms (Facebook, Instragram etc.) either via an ad or organically.

The value is expected to be low because the tag fires for everyone, but not everyone (as said by @jeppe_Nielsen) comes organically or from an ad click from Meta’s platforms.

I would check if this parameter value is saved successfully in the cookie when accessing the website with the fbclid parameter in the URL; and then do a conversion on another page checking if the data is received correctly by sGTM and passed on to Meta’s platforms.

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4

You are using Stape Data Tag + GA4 Client (default) , correct?

No, I am using GA4 Tag/Client and the Stape Facebook CAPI Tag :white_check_mark:

They are sent inside the common_cookie parameter in the Stape Data Tag. And they are a fallback if the values are not found in cookies.
For the GA4 Tag / GA4 Client (default) , only the cookies can be used as a source for the parameter.

ok, so common_cookie is only available with Data Tag/Client, ant it’s a fallback (so data Tag sends cookies twice?) :white_check_mark:

One question remains: Which cookies does GA4 Tag/Client send and receive? (I am guessing it is all 1PC)

I checked my setup, and all 1PC were sent by GA4 Tag, exept of _pin_unauth (Pinterest)

The fbc parameter is populated by the value of the fbclid URL parameter, which gets appended to the URL of your website (which in turn is saved into the cookie fbc )

Yes, I am aware :white_check_mark:

5

ok, so common_cookie is only available with Data Tag/Client, ant it’s a fallback (so data Tag sends cookies twice?) :white_check_mark:

Any tag that sends data to sGTM will carry the cookies in the HTTP request. It’s an inherent thing of the HTTP protocol and not of the tag per se.
So yes, the Data Tag can send cookies twice (but only if the cookie is on the Data Tag list of common cookies).

One question remains: Which cookies does GA4 Tag/Client send and receive? (I am guessing it is all 1PC)

All 1st party cookies, with a caveat (see below about cookie flags).

I checked my setup, and all 1PC were sent by GA4 Tag, exept of _pin_unauth (Pinterest)

Check if there are some different settings for this cookie flags. The SameSite flag in combination with the Secure flag can make the cookie not be sent depending on whether your sGTM is running under the same domain, but using a different subdomain as the main website.

6

Thank you, that makes it more clear!

So, Data Tag sends the 1PC with it (same as GA4 does) + sends all cookies from the list via eventData? (as an array of objects)

Check if there are some different settings for this cookie flags.

will do :white_check_mark:

7

So, Data Tag sends the 1PC with it (same as GA4 does) + sends all cookies from the list via eventData? (as an array of objects)

Partially correct.
In the eventData you’ll find them under the common_cookie key. It contains an object, where each property is the cookie name, and the value is the cookie value.

eventData.common_cookie = {
  _fbc: '_fbc cookie value',
  _fbp: '_fbb cookie value',
  _ttp: '_ttp cookie value', 
  // and so on
}
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