Google Analytics 4 (GA4) has Item List & Promotion reports. But, unlike Enhanced Ecommerce, no revenue or conversions are attributed back to Promotion or Item Lists (at the time of creating this solution).
This Variable Template for GTM (Web) makes it possible to attribute GA4 Item List, Promotion & Search Term to revenue or ecommerce Events (ex. purchase):
- Last Click Attribution
- First Click Attribution
- Reset/delete Attribution Data after Purchase
- Attribution Time (for how long should Item List or Promotion be attributed)
- Attribution Time can be either GA4 Session or Custom Attribution Time
A similar Variable do also exist for Server-side GTM. Differences between doing the attribution with GTM (Web) vs. Server-side GTM are listed below.
| Functionality | GTM (Web) | Server-side GTM |
|---|---|---|
| Cross (sub)domain tracking | No * | Yes |
| Server to Server-side (Measurement Protocol) | No | Yes |
| Attribution/processing | Users browser | Server-side |
| Storage Limitation | Yes | No |
| Costs Money | No | Yes |
* Cookies can do cross subdomain tracking, but are not very suitable due to very low storage capasity.
In the following documentation, Local Storage will be used to handle the attribution.
Install the following GTM (Web) Templates:
- GA4 - Item List & Promotion Attribution (this Variable Template)
- Local Storage Interact Tag
- Local Storage Checker Variable
We must create a decent number of Variables. Suggested Variable names are listed below, and are also used throughout the documentation.
- ecom - attribution time - minutes - C
- ecom - item_list & promotion - Local Storage
- ecom - item_list & promotion - extract - CT
- ecom - items - item_list & promotion - merge - CT
- ++
As standard, attribution time is the same as a GA4 Session, but you can choose a Custom Attribution Time if that better fits your users behaviour.
Create this variable if you are going to use Custom Attribution Time. Since attribution time is referenced in several variables, it’s recommended to create a Constant Variable with the attribution time in minutes. How long the attribution time should be is up to you. Time is counted from the last select_promotion, select_item or add_to_cart Event.
- Name the Variable ecom - attribution time - minutes - C.
We are using the Local Storage Checker to read data from Local Storage. For some unknown reason, this Variable doesn't allow any Key to be used without changing the Template, so for simplicity in this documentation we stick to one of the allowed Keys:
- Action: get
- Key: internal
- Name the Variable ecom - item_list & promotion - Local Storage.
Select the GA4 Ecommerce – Item List & Promotion Attribution Variable (this Template). This variable will extract Item List & Promotion data from GA4 Ecommerce and create the attribution. With other words, attribution happens at collection time.
- Variable Type: Extract Item Lists & Promotion for Attribution
- Data Sources
- Read GA4 Ecommerce data from Variable: Tick this box if you need to read GA4 Ecommerce data from a Variable.
- Second Data Source: {{ecom - item_list & promotion - Local Storage}}
- Attribution
- Delete Attribution Data after Purchase: Tick this box to delete/reset attribution data after a purchase has happened.
- You only need this setting for the Variable that attribute Items. Not necessary for Event-level attribution Variables.
- Custom Attribution Time: Tick this box if you are using Custom Attribution Time
- Attribution Time in Minutes: {{ecom - attribution time - minutes - C}}
- Measurement ID: Insert the same GA4 ID as you are using in the GA4 Configuration Tag. Note: This option is not visible if you have chosen Custom Attribution Time
- This setting uses GA4 Session as attribution time. GA4 Session value can be found in the _ga_<container-id> cookie, and Measurement ID is used to get information from that cookie.
- Attribution Type: Select Last or First Click Attribution
- Delete Attribution Data after Purchase: Tick this box to delete/reset attribution data after a purchase has happened.
- Site Search
- Search Term: Insert Variable that contains search_term value, ex. {{search_term - Query}}.
- Other Settings
- Handle data as string: This will save attribution data as a string. Tick this box with this setup.
- Limit Items: This will limit number of Items stored. You should probably limit number of items, but that is up to you. You can store up to 5MB in Local Storage.
- Name the Variable ecom - item_list & promotion - extract - CT.
Select the GA4 Ecommerce – Item List & Promotion Attribution Variable (this Template). This Variable merges Implemented data & data from Second Data Source (ex. Local Storage).
- Variable Type: Return Attributed Output
- Output: Items
- Remove null or empty values from Items: Check this box if your implementation have Item Dimensions with null, "null", "undefined" or empty values.
- Second Data Source: {{ecom - item_list & promotion - Local Storage}}
- Attribution
- Custom Attribution Time Tick this box if you are using Custom Attribution Time
- Attribution Time in Minutes: {{ecom - attribution time - minutes - C}}
- Measurement ID: Insert the same GA4 ID as you are using in the GA4 Configuration Tag. Note: This option is not visible if you have chosen Custom Attribution Time
- Custom Attribution Time Tick this box if you are using Custom Attribution Time
- Name the Variable ecom - items - item_list & promotion - merge - CT.
In addition, you must create Promotion & Search Term Variables using the same Variable Type if you have implemented Promotion without Items, or if you want to attribute Search Term:
| Variable Name | Output |
|---|---|
| ecom - location_id - merge - CT | Location ID |
| ecom - promo - creative_name - merge - CT | Creative Name |
| ecom - promo - creative_slot - merge - CT | Creative Slot |
| ecom - promo - promotion_id - merge - CT | Promotion ID |
| ecom - promo - promotion_name - merge - CT | Promotion Name |
| ecom - search_term - merge - CT | Search Term |
Create a Custom Event Trigger with the following settings:
- Event Name: ^(select_item|select_promotion|add_to_cart|purchase)$
- purchase Event in RegEx is only needed if you want to delete/reset attribution data after purchase
- Use regex matching: Tick the box
- *This trigger fires on: Some Custom Events
- ecom – item_list & promotion – extract – CT does not equal undefined
- Name the Trigger ecom - attribute Events.
Select the Local Storage Interact Tag, and add the following settings:
- Action: set
- Key: internal
- Value: {{ecom - item_list & promotion - extract - CT}}
- Add ecom - select_item, select_promotion & add_to_cart as a Trigger to the Tag.
-
- If you want to track search_term, add the same Trigger as you are using for tracking your view_search_results Event.
All GA4 Ecommerce Tags that should use attributed data have to be changed. These are the recommended GA4 Events:
- purchase *
- add_payment_info
- add_shipping_info
- begin_checkout *
- view_cart
- remove_from_cart
- add_to_cart *
- add_to_wishlist
- view_item
These Events are necessary for a complete GA4 Item lists: Item list name report *
The following Parameters should be changed in the Tags with those Events:
| Parameter Name | Value | Note |
|---|---|---|
| items | {{ecom - items - item_list & promotion - merge - CT}} | |
| promotion_name | {{ecom - promo - promotion_name - merge - CT}} | If Promotion without Items is implemented |
| promotion_id | {{ecom - promo - promotion_id - merge - CT}} | If Promotion without Items is implemented |
| creative_name | {{ecom - promo - creative_name - merge - CT}} | If Promotion without Items is implemented |
| creative_slot | {{ecom - promo - creative_slot - merge - CT}} | If Promotion without Items is implemented |
| location_id | {{ecom - location_id - merge - CT}} | If Promotion without Items is implemented |
| search_term | {{ecom - search_term - merge - CT}} | If you want to attribute search_term |
Your GTM (Web) setup is now complete.
To make the attribution work, also the implementation on the website must be correct. It’s especially implementation of Item List that can be incorrect.
All attribution in this solution is tied back to the following Events:
- select_item, add_to_cart (from a list) or select_promotion
When it comes to filling out the location_id parameter, if you don’t have Place ID as Google suggest using, fill this parameter with Page Path instead. Then you will get Page Path attributed as well.
The GA4 Event documentation allows for implementation of Item List and Promotion on both the Event-level and Item-level. This Template supports both implementations.
It’s recommended to implement all promotion parameters, but as a minimum for this attribution to work you must implement either promotion_id or promotion_name with the select_promotion Event.
The following Events should have Item List implemented. The rest of the ecommerce Events will read the Item List data from this Template.
Implementing Item List for the add_to_cart Event has though an exception. Item Lists should only be implemented if the Item is added to cart directly from an Item List.
You should never implement a Product Page Item List. The reason for this is that this will overwrite the Item List the user arrived from (ex. a “Related Products” list), and you will not be able to tell how well the “Related Products” list is working in terms of sales.
To make the attribution work, the GTM (Web) setup must also be correct.
In the examples below, the setup handles implementation both on the Event-level and Item-level.
In the setup you will see that Data Layer is mostly Version 1. The GA4 Ecom Items - DLV Version 1 Variable Template is used for achieving that.
This setup handles both select_promotion & view_promotion, where promotion also has Event-level Item Lists. location_id is set to Page Path.
This setup handles both select_item & view_item_list, with Event-level Item Lists. location_id is set to Page Path.
This setup handles add_to_cart & view_item. location_id in this setups is also Page Path, but Page Path will only be returned if item_list_name or item_list_id exist. Otherwise location_id will be undefined.
This solution can do either Last Click or First Click Attribution.
Attribution happens on 2 levels:
- Event-level
- Promotion without Items
- Search Term
- Item-level
- Implemented Items data (ex. Item List name) trumps attributed Items data. Ex. if you are adding a Item to cart directly from a Item List, the implemented Item List Name will be used. If you are adding the Item to cart from a product page (where you shouldn't have a Item List implemented), the attributed Item List Name will be used.
- Item-level trumps the Event-level.
- Promotion without Items will not be attributed to a Item when Promotion with Items are attributed
To get a better understanding of the attribution, it's recommended to run some test scenarios where you inspect your own data:
- Run GTM (Web) in Preview Mode
- Look at the Local Storage data being built or rewritten
- Inspect especially Items in GA4 DebugView
With a Last Click Attribution model, this user journey illustrates the attribution:
- User clicks on “Promotion 1 without Items” (promotion without any Items attached to the promotion). This is an Event-level promotion, and “Promotion 1 without Items” is the attributed Event-level promotion.
- On the “Promotion 1 without Items” page, there is a “Promotion 2 without Items” promotion, and the user clicks on the promotion. This promotion is also an Event-level promotion. “Promotion 2 without Items” is now attributed to the Event-level promotion.
- The user clicks next on a promotion for a bundled phone with earbuds package (“Promotion 3 with Items”). This promotion has 2 items attached, the phone and the earbuds. This promotion is attached to the 2 different Item Id’s (item_id = phone1 and item_id = earbud2) and is therefore an Item-level promotion.
- User adds this bundle with 2 items to cart. The add_to_cart Event is attributed to the promotion.
- User clicks after that on the “Users Also Looked At” Item List with other earbuds that it’s also possible to choose. The earbud (item_id = earbud3) the user clicked on is attributed to the “Users Also Looked At” item list.
- On this page, there is also an “Users Also Looked At” item list. User clicks on the first selected earbud (item_id = earbud2). The earbud is now attributed to the “Users Also Looked At” item list and is no longer attributed to the initial Item-level promotion.
- User completes the purchase, and GA4 adds some logic to the result, namely that Item-level trumps the Event-level.
- The phone (item_id = phone1) is attributed to the “Promotion 3 with Items” promotion. The promotion didn’t have any Item List, so no Item Lists are attributed. If the promotion also had an Item List, this list would have been attributed.
- The earbud (item_id = earbud2) is attributed to the “Users Also Looked At” item list, but in addition, since this item doesn’t have any Item-level promotion, the Event-level promotion “Promotion 2 without Items” is also attributed to the earbud.
- Since Item-level trumps Event-level, “Promotion 2 without Items” is not attributed to the phone, since this has an Item-level promotion attributed.
In the same scenario, but using First Click Attribution, this would be the result:
- Both the phone (item_id = phone1) and the earbud (item_id = earbud2) would both be attributed to the Item-level “Promotion 3 with Items” bundle promotion.
- “Users Also Looked At” item list would not be attributed to the sale.
- None of the Event-level promotions “Promotion 1 without Items” or “Promotion 2 without Items” would be attributed since Item-level trumps Event-level.