Last Click vs Data-Driven Attribution

One of the fundamental, often-overlooked factors behind understanding your results is your attribution setting. Attribution determines which ad clicks get the credit for conversions—like purchases, signups, or leads—so you can see what's really working.

But here’s the catch: even if you have conversion tracking set up, you might not really know how your account is attributing those conversions. That’s where the choice between Last Click Attribution and Data Driven Attribution comes into play.

Let's break down both attribution models, their pros and cons, who should use them, and even show you how to compare them in your own Google Ads account. 

What is Attribution in Google Ads?

Attribution is a fancy word for a simple idea: who gets the credit for a conversion?

Let’s say you’re running Google Ads for your online store. Someone clicks your ad on Monday, but doesn’t buy. They click another ad of yours on Thursday, still no sale. Then, finally, they click one more of your ads on Saturday and make a purchase. Which of those ads—Monday's, Thursday's, or Saturday’s—should get the pat on the back?

The answer depends entirely on your attribution model.

“In Google Ads, there's different attribution methods that you could use that helps you determine which advertisement or which campaign gets the credit for that conversion.”

Attribution models control two things:

• How credit for conversions is assigned across multiple ad interactions

• How you judge the success of your campaigns, ad groups, and individual ads

There are several attribution models in the Google Ads toolbox, but the two you’ll see most often are Last Click Attribution and Data Driven Attribution. Let’s break them down.

Last Click Attribution: The Simple, Default Approach

How Last Click Attribution Works

Last Click Attribution gives 100% of the credit for a conversion to the last ad click that the user made before converting. That’s it. If there were three ad clicks in the customer’s journey, the last one is the winner—every time.

Let’s walk through an example:

• Monday: Jane clicks your “Summer Sale” ad, browses your site, but doesn’t buy.

• Wednesday: She clicks your “Free Shipping” ad, but again, leaves without buying.

• Friday: Jane clicks your “Final Day Deals” ad and makes a purchase.

If your account is set to Last Click Attribution, Friday’s “Final Day Deals” ad gets 100% of the conversion credit. The other two ads? Nada.

“Last Click attribution gives 100% of the credit to that final ad click in the process. ... that third and final click would receive 100% of that credit. Clicks one and two wouldn't get anything.”

Last Click Attribution is:

• Simple to set up

• Easy to understand

• The historical default for Google Ads (although this is rapidly changing)

Above: An example of Last Click Attribution—only the final click gets credit.

When to Use Last Click Attribution

• You want a no-nonsense approach and don’t care about the customer journey or earlier clicks.

• Your sales cycle is short: People usually buy right after clicking (like a restaurant, local business, or time-limited offer).

• You’re just starting out with Google Ads and don’t have a large amount of data.

Last Click is often seen as a “set-and-forget” model, especially for small advertisers or those with simple offerings.

Limitations of Last Click Attribution

Here’s the major downside:

• You miss out on the impact of earlier ad interactions.

• If that first or second ad click was what introduced the customer to your business, wouldn't you want to know?

• Top-of-funnel campaigns and discovery ads are undervalued, even if they’re important in a multi-step journey.

“The main con for last click attribution is any of the previous ad clicks that led to that conversion get 0% credit. And those clicks might have been very important in that customer's journey to make a purchase.”

In recent years, Google has steered more advertisers away from Last Click—and for good reason. There’s a smarter way to track conversions if you have the data for it.

Data Driven Attribution: Smarter Credit for Every Click

How Data Driven Attribution Works

Data Driven Attribution (DDA) is Google’s most advanced, default attribution option. It uses machine learning to look at your actual conversion data and assign credit across various clicks based on their predicted contribution.

“It uses machine learning to analyze all of your conversion data, including clicks, to determine how much credit each ad interaction actually contributed to the conversion.”

Let’s revisit Jane’s example:

• First ad clicked: “Summer Sale”

• Second ad clicked: “Free Shipping”

• Third ad clicked: “Final Day Deals” (and purchase)

Instead of 100% of the credit going to the last click:

• The first click might get 25%

• The second click 25%

• The third click 50%

Above: Data Driven Attribution gives credit to every click along the journey, not just the last one.

This approach spots patterns in your data, such as:

• Do some ad campaigns start a lot of journeys but rarely close the sale?

• Are certain keywords or ad groups crucial “assistants” rather than “closers”?

When to Use Data Driven Attribution

• You have a high-traffic account, with lots of conversions and clicks to feed Google’s algorithms.

• You run campaigns at different funnel stages: top-of-funnel discovery, mid-funnel consideration, and bottom-funnel conversion ads.

• You want to value the full customer journey and optimize for all impactful touchpoints, not just the last click.

“If you are above that 200 conversion level, in that 2000 ad interaction level ... the difference between the Data Driven Attribution and the last click attribution, it's not a ridiculously high number ... But I actually think that Google does a good job in keeping the comparison apples to apples instead of apples to oranges.”

Requirements for Data Driven Attribution

Well, it can’t work magic without data.

• You need at least 200 conversions and 2,000 ad interactions (clicks) in a 30-day period—even more is better.

• That makes DDA a bad fit for many smaller accounts or advertisers just getting started.

“Google recommends that you have over 200 conversions in 2000 ad interactions within a 30 day period. So for a lot of small businesses, Data Driven Attribution, at least at this point of time, isn't in the cards.”

Above: DDA requires significant data to make effective, accurate attributions.

Challenges and Transparency

Data Driven Attribution isn’t perfect.

• It’s a bit of a black box: Google doesn't show you exactly how the split is calculated for each conversion.

• You might wonder, “Why did this keyword/campaign get more or less credit?” Sometimes, there isn’t a clear answer except “the data says so.”

• Not all conversions or goals are eligible for DDA (based on volume).

Still, if you have the data, DDA gives a richer, more nuanced understanding of your advertising funnel. You’ll discover which campaigns, keywords, or even ad groups are quietly playing a big role.

A Step-by-Step Walkthrough: See Your Attribution Models in Google Ads

Let’s take things from theory to practice. Ever wonder which of your conversion goals is using last click or DDA? Or want to compare what would happen if you changed your attribution model?

Here’s how to do it—step by step.

Accessing the Attribution Comparison Tool

1. Log in to your Google Ads account.

2. On the left menu, select “Goals” (under the 'Tools & Settings' tab).

3. Then under “Measurement”, click “Attribution”.

4. You’ll see the Attribution screen. Here’s where you can select “Switch to DDA” to get a status update of all your different conversions and their associated attribution models.

Reading the Comparison Results

You’ll see a table showing:

• Which conversion actions are using DDA

• Which ones aren’t eligible

• Side-by-side comparisons of conversions by attribution model

You can filter by campaign type, campaign, ad group, or even keyword level to see exactly how your conversion numbers would look under each model.

“You can filter by different dimensions. So right now I've got it on campaign type, but you can actually select Campaign or even Ad Group or even keyword if you want and it gives you a simple table that shows how many conversions that campaign type had on Last click and how many conversions that campaign type would have had on Data Driven.”

Above: The Attribution Model Comparison Tool in Google Ads.

This transparency lets you eyeball:

• Are there major differences in how many conversions are assigned to each campaign/ad group/keyword under DDA vs. Last Click?

• Are top-of-funnel campaigns actually playing a bigger role than Last Click would have you believe?

What Model Should You Pick? Recommendations by Account Type

Choosing between Last Click Attribution and Data Driven Attribution depends on your unique account setup, data volume, and business goals.

Here’s how to decide:

Go with Data Driven Attribution if:

• You have the volume: Over 200 conversions and 2,000+ ad clicks in 30 days, consistently

• You’re actively optimizing and want to make data-backed decisions for all stages of your funnel

• You run complex ad campaigns: multiple funnel stages, retargeting, search plus display, etc.

• You want better insights into how different campaigns, ad groups, or keywords assist conversions, not just “close” them

Stick with Last Click Attribution if:

• You’re a small business looking for something simple: Getting fewer conversions and limited traffic at this stage

• You’re new to Google Ads: Focus on simplicity until you accumulate more data

• Your sales cycle is very short: One click, one purchase; multi-step tracking unnecessary

“If you're a small business or a new Google Ads account that you're just getting started, stick with Last Click Attribution while it's still available.”

How Big Are the Differences in Practice?

You might wonder—will switching attribution models give dramatically different results?

In many cases, the difference is noticeable but not huge. For example, in a real-world account, changing from Last Click to DDA made less than a 1% difference in conversions for search and display campaigns.

“In this account the change from Data Driven Attribution to Last click. It's not a material amount. On the search campaigns it's a minus 0.23% difference and then on display its 0.22% different.”

Every account is unique, though. Your mileage may vary, especially if you have a diverse set of campaigns at different funnel stages.