On the path to conversion, customers may interact with multiple ads from the same advertiser. Attribution models let you choose how much credit each ad interaction gets for your conversions.
Attribution models can give you a better understanding of how your ads perform and can help you optimize across conversion journeys.
This article describes the various attribution models and how to use them in Google Ads. You'll learn how to set an attribution model for conversion tracking and bidding, and how to compare models with the "Model comparison" attribution report.
Most advertisers are used to measuring the success of their online advertising on a "last click" basis. This means they give all the credit for a conversion to the last-clicked ad and corresponding keyword. However, this ignores the other ad interactions customers may have had along the way.
Attribution models give you more control over how much credit each ad interaction gets for your conversions. This allows you to:
- Reach customers earlier in the purchase cycle: Find opportunities to influence customers earlier on their path to conversion.
- Match your business: Use a model that works best for how people search for what you offer.
- Improve your bidding: Optimize your bids based on a better understanding of how your ads perform.
About the different attribution models
Google Ads offers several attribution models:
Last click: Gives all credit for the conversion to the last-clicked ad and corresponding keyword.
First click: Gives all credit for the conversion to the first-clicked ad and corresponding keyword.
Linear: Distributes the credit for the conversion equally across all ad interactions on the path.
Time decay: Gives more credit to ad interactions that happened closer in time to the conversion. Credit is distributed using a 7-day half-life. In other words, an ad interaction 8 days before a conversion gets half as much credit as an ad interaction 1 day before a conversion.
Position-based: Gives 40% of credit to both the first and last ad interactions and corresponding keywords, with the remaining 20% spread out across the other ad interactions on the path.
Data-driven: Distributes credit for the conversion based on your past data for this conversion action. It's different from the other models, in that it uses your account's data to calculate the actual contribution of each interaction across the conversion path. The "Data-driven" model is the default attribution model for most conversion actions. Learn more about data-driven attribution
You own a restaurant called Ristorante Abigaille in Florence, Italy. A customer finds your site by clicking on your ads after performing each of these searches: "restaurant tuscany," "restaurant florence," "3 star restaurant florence," and then "3 star restaurant abigaille florence." She makes a reservation after clicking on your ad that appeared with "3 star restaurant abigaille florence."
- In the "Last click" attribution model, the last keyword, "3 star restaurant abigaille florence," would receive 100% of the credit for the conversion.
- In the "First click" attribution model, the first keyword, "restaurant tuscany," would receive 100% of the credit for the conversion.
- In the "Linear" attribution model, each keyword would share equal credit (25% each) for the conversion.
- In the "Time decay" attribution model, the keyword "3 star restaurant abigaille florence" would receive the most credit because it was searched closest to the conversion. The "restaurant tuscany" keyword would receive the least credit since it was searched first.
- In the "Position-based" attribution model, "restaurant tuscany" and "3 star restaurant abigaille florence" would each receive 40% credit, while "restaurant florence" and "3 star restaurant florence" would each receive 10% credit.
- In the "Data-driven" attribution model, each keyword would receive part of the credit, depending on how much it contributed to driving the conversion.
To learn how to compare these attribution models and see how they'd affect your data, see the section on the "Model comparison" report below.
About attribution models for conversions and bidding
The "Attribution model" setting in conversion tracking lets you decide how to attribute conversions for each conversion action. You can use this setting for website and Google Analytics conversion actions. Learn how to set an attribution model for your conversions
This setting affects how conversions are counted in your "Conversions" and "All conversions" columns. (Keep in mind that the "Conversions" column only includes those conversion actions you've marked as primary conversions.) For example, if you choose "First click" as your attribution model, conversions will be credited to the first ad customers clicked before completing a conversion. In your reports, the conversions would count in the campaigns, ad groups, ads, and keywords associated with the first-clicked ad.
The attribution model you choose only affects the conversion action to which it's applied. The setting also affects any bid strategies that use the data in the "Conversions" column. This means that if you use an automated bid strategy that optimizes for conversions, such as Target cost per action (Target CPA), Enhanced cost-per-click (ECPC), or Target return on ad spend (Target ROAS), the attribution model you select will affect how your bids are optimized.
If you use manual bidding strategies, you can change your attribution model to help you set your bids.
If you're not sure what model to choose, see the section below on the "Model comparison" report, which lets you compare different attribution models. When you're trying a new non-last click attribution model, we recommend that you test the model first and see how it affects your return on investment.
About the "Model comparison" report
The "Model comparison" report lets you compare two different attribution models side-by-side. To find keywords, ad groups, campaigns, or devices that are undervalued on a last-click basis, you can start with the following comparisons:
- Compare the "Last click" model to the "First click" model to identify undervalued keywords that are starting customers down the conversion path. This is particularly valuable if you're looking to drive more new customers to your website.
- Compare the "Last click" model to the "Linear" model to identify undervalued keywords that are assisting customers all along the conversion path. This is particularly valuable if you want to stay in touch with customers throughout their purchase process.
- Compare the "Last click" model to the "Data-driven" model to see the value of keywords as determined by Google's machine-learning model, which looks at how your customers convert to allocate credit. Data-driven attribution also gives you a sense of the value of ad interactions along the entire conversion path.
Tip: Analyze your CPA or ROAS for different attribution models
You can use the "Cost / conv." and "Conv. value / cost" columns in the "Model comparison" report to compare your CPA and ROAS for different attribution models. This allows you to identify campaigns or keywords that are undervalued using the "Last click" attribution model. You can then change your bids based on the actual value of your campaigns and keywords across the full conversion path.
How to find and set an attribution model for your conversions
You can set the attribution model when you're setting up your conversion action, or follow the instructions below to compare attribution models and change the attribution model for an existing conversion action:
Compare attribution models
- Sign in to your Google Ads account.
- In the upper right corner of your account, click the tools icon , then under “Measurement,” select Attribution.
- In the page menu on the left, click Model comparison.
- Select an option from the "Dimension" drop-down menu.
- Use the "Compare" and "With" drop-down menus to select the attribution models you want to see and compare.
You can search for specific keywords, ad groups, campaigns, or accounts from the search box above the table.
Change the attribution model for an existing conversion action
- Sign in to your Google Ads account.
- In the upper right corner of your account, click the tools icon , then under "Measurement," select Conversions.
- In the table, select the conversion you want to edit by clicking the conversion name.
- Click Edit settings.
- Click Attribution model, and select an attribution model from the drop-down menu.
- Click Save, and then click Done.
Cross-account conversion tracking
If you use cross-account conversion tracking to track conversions at the manager account level, you must select your attribution model in the manager account.
Attribution models in your reporting columns
When you change the "Attribution model" setting for a conversion action, it only changes the way your conversions are counted in your "Conversions" and "All conversions" columns going forward. If you want to see how your historic conversions data would look with the attribution model you've just selected, you can add the "current model" columns (located in the "Attribution" section of the "Columns" menu):
- Conversions (current model)
- Cost / conv. (current model)
- Conv. rate (current model)
- Conv. value (current model)
- Conv. value / cost (current model)
- Conv. value / click (current model)
- Value / conv. (current model)
These columns can be helpful if you've just changed your attribution model and you want to get a sense of how it will affect your conversion data. You can compare these columns to your regular conversion tracking columns to see how your data would have differed if you'd been using the attribution model you've now selected.
Like the regular "Conversions" columns, these columns won't include any conversion actions that you've chosen not to mark as primary conversions. However, cross-device conversions are included by default.
Keep in mind that these columns include data that isn't affected by your attribution model selection, such as data from Display Network campaigns using pay for conversions billing.