You will typically begin importing your existing implementation during the property creation process. However, if you did not complete the Map Existing Implementation step while creating your Apollo property, you can access the module via the button in the upper right of Property Settings.

To import your existing Google Tag Manager (GTM) implementation into Apollo, you first have to establish a Google Cloud API connection. This connection will allow Apollo to import the events and variables in your established GTM container. If you are beginning the Map Existing process for a new Apollo property during the Property Creation flow, you will establish your API connection in an earlier step. If you are beginning the process for an existing Apollo property from the Property Settings, ensure you have a successful API connection under the Connections card.

During the property creation process, you will be asked if you'd like to Map an Existing Implementation.

Clicking No, I'm done will complete the property creation process and disable the Map Existing Implementation module for your property now and in the future. All configurations for your Apollo property will take place in the Design module.

Clicking Yes will allow you to select the GTM Container and Container Version you would like to map to your Apollo property.

When selecting your version, you will notice that the latest version of your GTM container is appended with the latest flag.

Once you have selected your container and version, click Import. This initiates the import process. At this time, all other design features, such as Business Requirements and Apollo Event Attributes, go into read-only mode until you complete the map existing implementation process. If you decide against mapping your existing implementation, you can click Never Mind to return to the Map Existing confirmation dialog.

After you have imported the desired GTM container from property creation, you will be redirected to the Map Existing Implementation view.

If you are mapping your implementation across multiple visits, you will see a banner in your Apollo property indicating that the Design features are unavailable. These features will remain unavailable until you have finished mapping your implementation. You can return to the Map Existing Implementation module by clicking Take me there.

Additionally, you can access the Map Existing Implementation feature by visiting Property Settings and clicking Map Existing Implementation in the upper right of the modal.

In the Map Existing Implementation module, you will see a list of tags configured in the GTM Container you have imported. Please keep in mind, only Universal Analytics tags can be mapped in Apollo. If at any time you would like to restart the mapping process, click the Start Over button. This removes all previous mappings you have made and allows you to select a different GTM container and version to map from. If you have multiple API connections associated with your Apollo property, you may also select the connection you would like to use.

Above the tag table, you will also see the ratio of tags you have included in your mapping over the total number of tags available to map.

At anytime you can filter the existing tags list to see those that are mapped or unmapped. Additionally, the open search field allows you to search the table for existing tags by Tag Name.

Using the Apollo Event column, look for an Apollo event that corresponds to the tag you would like to import. For example, if you have a tag, Form Started, in your current implementation, a search for form in the Apollo Event dropdown shows various “form” related events available in Apollo. When you find a match, select it to map your current tag to the corresponding Apollo event.

Note: If there are “out-of-the-box”/platform built-in data points associated with your implementation, they will not be shown on the Map Existing Implementation screen. These are automatically mapped and included in your implementation.

Once you have selected a corresponding Apollo Event, the tag is enabled and the other options become available for configuration.

If the tag you are mapping requires the GA4 Configuration tag, then check the box in the Requires Config Setup Tag column. The configuration tag defines attributes that will be sent with all tags that fire after it.

If you would like to use the trigger(s) in your existing implementation associated with the tag you are mapping, you can make that selection under the Use Existing Trigger dropdown. This ensures the Apollo event is associated with your existing tigger(s), instead of the Apollo trigger. However, if you would like to use the Apollo defined trigger, leave this option blank.

To save the selections and updates you have mapped click the Save Changes button in the floating footer. If you exit or refresh the Map Existing Implementation module without saving, all unsaved changes will be lost. To undo any unwanted modifications since your last save, you may click Revert Changes in the floating footer.

Apollo utilizes the Page Load Started event for the GA4 Configuration Tag, since the configuration tag fires at the start of every page before any other event tags. If you would like to map your existing GA4 Configuration Tag, simply select Page Load Started from the Apollo Event dropdown and continue mapping.

To map the attributes associated with your tag, click the Configure Tag Attributes button. Doing so will open the the tag attributes configuration modal.

In the tag attributes modal, you will see a list of all of the attributes associated with the tag you are mapping. The name of the tag you are currently mapping is displayed in the upper left of the window. You will also find the ratio of mapped parameters to total parameters there. Additionally, you may filter the attributes list and search by Attribute Name.

Using the Apollo Variable Name column, look for the corresponding Apollo variable. Once you have selected the equivalent Apollo variable, your attribute will be enabled. When you have completed your configurations, click Save Changes in the floating footer. You must save your mappings before returning to the tag configuration view, or your changes will be lost.

If you don’t find a corresponding Apollo event or variable that matches the tags or attributes in your current implementation, please reach out to the Apollo team who can help determine if what you are looking for already exists.

If you would like to use the GTM variable assigned to the attribute in your existing implementation, check the box in the Use Existing GTM Variables column. This ensures Apollo sets the attribute's value to the existing GTM variable, instead of the associated Apollo variable. If you would like to use the Apollo defined variable, do not select this option.

Alternatively, you may use the All Mapped and None buttons in the upper right. When you click All Mapped, Apollo will automatically check the Use Existing GTM Variable option for all enabled attributes. Conversely, clicking None will disable the option for all enabled attributes.

The screen capture above was taken after All Mapped was clicked. Notice that the Use Existing GTM Variable option was not enabled for dimension1, as that attribute had not yet been mapped to an Apollo variable. However, dimension5 and dimension6 were mapped, so the option was enabled.

As you map your GTM tags and attributes to the corresponding Apollo events and variables, Apollo is enabling the related business requirements behind the scenes. Additionally, Apollo is generating the data layer specification for the implementation you are building. You should continue this process for all of the items in your current implementation that you wish to carry forward to your new Apollo property.

Once you are done with your configurations, click All Mappings Complete. Please ensure that you are completely satisfied with your mappings, as you won't be able to make changes after you've completed the map existing process.
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Congratulations! You've finished mapping your existing GTM Container to your Apollo property. Now you can take advantage of the rest of Apollo's features.