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Sending custom parameters to Google Ads conversions
Jeff Sauer
October 16, 2025
In partnership with
Here's how to give Google the data it actually needs
Your Google Ads conversions just got a major upgrade.
Google Tag Manager quietly rolled out a feature that's been years in the making. You can now send custom event parameters to your Google Ads conversions without touching a single line of code.
This matters more than you think.
The Problem We've All Been Living With
For years, we've been sending Google the equivalent of postcards. "A sale happened." "Someone filled out a form." That's it.
Meanwhile, we know so much more. Which leads are actually qualified. What product categories perform best. Which subscription tiers convert to long-term customers.
All of that context? It stayed locked in our internal systems while Google's bidding algorithm operated half-blind.
What Changed
Alina, one of our MeasureU mentors, discovered this update while working on a client setup. Instead of requiring developers to hardcode gtag.js snippets, you can now use your existing GA4 data layer to send additional parameters through Tag Manager.
The technical barrier is gone.
Think of it this way: Instead of telling Google "10 conversions happened," you can now say "3 premium subscriptions, 4 basic plans, and 3 qualified enterprise leads happened."
The Lead Quality Breakthrough
Here's where this gets interesting for lead generation.
Instead of treating all form submissions equally, you can send lead quality scores as custom parameters. A basic contact form and a qualified enterprise inquiry no longer look the same to Google's bidding algorithm.
On our latest podcast episode, Alina showed me how she's implementing this for clients. They're using lookup tables in Tag Manager to assign values based on lead scores, then feeding that into maximize conversion value bidding.
The algorithm finally knows which leads actually matter.
The Implementation Reality
The setup is straightforward if you already have proper data layer implementation:
Add event parameters to your Google Ads conversion tag in GTM
Register the custom variables in your Google Ads account (this step trips people up)
Wait for data to populate (it's not retroactive)
Use the parameters for segmentation and optimization
But here's what Alina learned the hard way: You have to register each custom variable manually in Google Ads. It doesn't automatically appear just because you set it up in Tag Manager.
What Not to Send
Don't get clever with sensitive data. No personal identifiers, no profit margins, nothing you wouldn't want visible in browser developer tools.
And don't try to recreate existing functionality. Enhanced conversions, new vs. returning customers, lifetime value - these already have dedicated fields. Use what’s baked into the platform in those cases.
Why This Matters Now
The advertising landscape shifted when third-party cookies started disappearing. Platforms have less data about users than ever before.
Sharing your first-party data with ad platforms is your competitive advantage.
Google can't read your mind about what makes a good customer. You have to tell them. The more context you provide, the better they get at finding similar people.
This isn't just about more granular reporting (though you get that too). It's about training smarter algorithms.
The Bigger Picture
We're in an era of advertising where data setup matters as much or more than campaign optimization. The platforms handle most of the bidding decisions now.
Your job shifted from manual bid adjustments to feeding the machine better information.
Most advertisers are still treating this like 2015. Set up basic conversion tracking and hope for the best.
The ones getting results are treating their ad accounts like analytical tools. They're sending rich, contextual data and letting the algorithms do what they do best.
Start Simple
Alina's advice: Don't implement 10 variables at once.
Pick one or two high-impact parameters. Maybe subscription tier. Maybe lead source quality. Something you already have in your data layer.
Implement it. Validate it. Get comfortable seeing it in your reports.
Then build from there.
The platforms are getting smarter. Make sure you're feeding them the intelligence they need to work for you.
To Your Measured Success!
--Jeff Sauer
Co-Founder of MeasureU
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