Implications of Duplicate Records in Marketo

Marketo Employee
Marketo Employee

Definition of Duplicates

Marketo defines duplicates as two or more records having the same email address. 


How would different aspects of Marketo be affected by having Duplicates:


Sending Batch Emails

If there are duplicates, only 1 email will go out. It will be the lowest Marketo ID. This record is also used to populate tokens. Example:


Marketo ID

First name







In this case, the email will be sent to the first record with Lead ID 2749. It will say “Dear Elizabeth” if you use a token for first name. Also, the activity entries will be attached to that record (sent, delivered, opened, clicked). When the email click goes to a page with Munchkin code in it, any web visits will also be associated with this record. Then, this record will be the cookied record.


Sending Trigger Emails

The record (one of the duplicates) which triggered the triggered campaign, will be sent the email. Also, the activity entries will be attached to that record (sent, delivered, opened, clicked).


Form Fill-outs

If someone fills out a form and their email address is in Marketo multiple times, the form submissions are applied to the record that is already cookied, or – if not yet cookied – it will be applied to the most recently updated record. The most recently updated record is determined by the last modified date that is in the “Updated At” field.


Web Visit Tracking

The Marketo munchkin code generates a cookie with a unique ID for each web browser. This ID can be linked to exactly 1 Lead in Marketo. So, if there are duplicates, the web activity will be linked to only 1 of the duplicates. The cookie can be linked to this record in one of two ways:

  • Clicks link in email, and the link goes to a page with Munchkin installed  the duplicate that received the email will be cookied
  • Fills out form  the duplicate with matching Cookie ID, or otherwise the most recently updated duplicate


List Uploads

When an email address is included in a list import, it attaches to the most recently updated record in Marketo.


Unsubscribed, Marketing Suspended, etc.

The standard “Unsubscribed” field will be kept in sync across duplicates via the ‘durable unsubscribe’ functionality. However, “Marketing Suspended”, “Email Invalid” and “Blacklisted” are not kept in sync and could have different values across duplicates.


Marketo Engage Technical Consulting Team has a custom solution to keep person fields between duplicates in sync. Connect with your CSM to know more about this.



There may be an impact on reporting if there are duplicates in your Marketo system. There are many types of reporting, so the impact may vary. For email reporting, you will see the results for the record that received the email, so there is no impact there. If you report on total number of Leads, the duplicates will be included in the total counts. If you do ROI reporting, the last modified record is most likely associated with the Opportunity, but it’s not 100% sure. For Revenue Cycle reporting, it’s again most likely the last modified record that will progress through the cycle.



Obviously, the fewer duplicates, the better. We encourage all our customers to strive to eliminate duplicates in Marketo. However, if there are some duplicates in your system, it is likely that most functionality will still work correctly, or at least it should have only a small impact.


If you want to merge duplicates in your Marketo instance, please connect with your CSM to know about the duplicate merge solution Marketo Technical Consulting Team has built.

Level 4 - Champion

@AmritTandon - Another important thing I've found for those using workspaces and partitions is that the form-fill behavior works the same even across partitions.  For example, if you have NOAM and EMEA partitions and matching workspaces, and you have a duplicate lead in both partitions (  Even if your landing page and form are in your NOAM workspace, the "last updated" record will be updated. So if the in the EMEA partition was last updated, that is the record that will change and have the form fill activity.  I believe having support add a custom dupe key using email + partition will fix this.

Level 3

Yeah, but WHY is there  a duplicate? If I upload a list of emails as identifiable spam for deletion... and I delete all the individuals on that list, will the original lead be delated as well?

Level 4

Duplicates cause so many headaches.  In many cases the duplicates are caused on the CRM side which can be difficult to control for some organizations.  Putting together a solid CRM governance process and rule sets are absolutely key to control the bleeding as well as training for the teams using the CRM to actually "CHECK" to see if a person already exists before creating a new record.