Question from Reddit user:
Hi everyone,
I’m currently facing an issue with passing custom parameters (custom variables in Google Ads) from Google Tag Manager (GTM) to a Google Ads using GADS Conversion Tracking Template — specifically for a “Registration Complete” event.
I’m trying to send additional form data to Google Ads, including:
Country Name
Business Category Type
(both are values selected from dropdowns in the registration form)Here’s what I’ve done so far:Created a custom JavaScript variable in GTM to pull the values from the dataLayer.
Set up a Google Ads Conversion tag to fire on the registration completion.
Tried adding these custom variables to the tag, but it seems Google Ads isn’t receiving them.
FYI Conversion tracking template now don’t support custom parameters anymore (link info: https://trackingchef.com/google-ads/custom-variables-google-ads-conversion/#:~:text=1,data%20you%20want%20to%20send / and this one: https://seekandhit.com/tracking/custom-variables-for-gads-conversions-through-ga4/#:~:text=It%20seems%20that%20currently%20there,would%20be%20a%20no%20brainer)
From what I’ve read, the standard Google Ads Conversion Tracking tag in GTM no longer support sending custom parameters directly. I’ve also experimented with using gtag (auto-updated version), but still no luck — Google Ads doesn’t seem to pick up the values.
Has anyone here successfully implemented something similar through GTM for Google Ads custom variable? Would love to hear if you’ve run into this and how you solved it.
Thanks in advance
Answer from Nabil:
The short answer is:
You are correct. The official Google Ads Conversion Tracking tag template in GTM no longer reliably supports custom parameters sent client-side via the tag’s interface.
Google is moving away from this older method, prioritizing privacy-compliant, server-side data ingestion.
The most effective, resilient, and future-proof solution is to use the Google Ads API via a server-side tagging setup like Stape or Google Cloud Platform.
You would capture the form data and the Google Click ID (gclid) on the client, send it to your server-side GTM container, and then have the server directly call the Google Ads API to report the conversion with all the required custom variables, bypassing the need for the client-side conversion tag entirely.
The long answer is:
Your struggle is entirely understandable, and your research has pinpointed the core issue: the direct transmission of custom parameters through the old Google Ads Conversion Tracking tag template in GTM has become unreliable and is not the intended path forward for detailed conversion tracking, especially with the industry’s shift towards better data privacy and first-party data.
The reason your custom variables, such as Country Name and Business Category Type, are not showing up is because the underlying client-side gtag implementation for conversions is not designed to accept arbitrary custom parameters for the Google Ads platform in the way that the Google Analytics 4 event tag does.
The client-side method is prone to failure from ad blockers, network interruptions, and browser privacy restrictions.
The modern, robust solution that guarantees data transmission and eliminates reliance on the user’s browser is to switch to a server-side tracking model using the Google Ads API.
The process would look like this: You first ensure that when the user registers, your client-side GTM container captures all the necessary information, including the form data and the crucial Google Click ID (gclid) from the URL or a persistent cookie.
Next, you set up a server-side GTM container (hosted on Stape or GCP).
When the Registration Complete event is triggered on the client, instead of firing the Google Ads Conversion tag, you send a single, comprehensive data request to your server container.
Your server container then uses a server-side tag, or a custom script, to perform an immediate Google Ads API call.
This call sends the conversion data, the Google Click ID, and all your custom parameters (Country Name, Business Category Type) directly to the Google Ads system.
Because you are using the Google Ads API (specifically the Conversion Upload Service), you have complete control over the payload and are guaranteed to bypass all client-side restrictions and delays.
This is essentially the mechanism that Google now encourages, often referring to it as Enhanced Conversions or Server-Side Tracking, and it is the most reliable way to ensure that your valuable custom form data makes it into Google Ads for accurate bidding and optimization.
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