How To Troubleshoot List Imports

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When uploading subscribers to a new or existing list in Klaviyo, your list may fail to upload. If this occurs, you will see that a certain number of records were skipped. Often, this is the result of a small error. In this article, you will learn common troubleshooting tips to overcome this roadblock and upload your list successfully.


Want to make sure your file will import? Check the list below before importing your list.

  • CSV File (not any other format)
  • File size is 50 MB or fewer
  • First row is headers
  • First column is email addresses
  • Every row has an email address associated with it
  • No duplicate email addresses
  • All email addresses are formatted properly

Our Support Team is not able to import CSVs into Klaviyo on your behalf. If you need help with an import, please check out the troubleshooting section below for tips and tricks on how to successfully troubleshoot list import issues.

Import Delay

If you import a large file with a significant amount of data, the import process may take several hours to complete. Unfortunately, there is no way to speed up this process. We highly recommend planning to import a new list at least one day in advance of when you intend to email the list.

After an import begins, you will initially see a status bar. If you click away, you will otherwise be able to track the import’s progress by watching the list count increase over time. We will send you an email as soon as a list import completes.

Import Troubleshooting

If your list fails to upload, look for the following common errors in your CSV file that may be causing this roadblock:

Improper CSV Formatting

Your file must be a CSV file, not an Excel file or TSV. You can save any Excel file as a Comma Separated Values (.csv) file by clicking File > Save As and adjusting the file format. If you are using a version of Excel that does not use English as the default language, your software may use semi-colons and not commas in an export.

To remedy this, head to your computer's Language & Regional Settings > Advanced Settings > List (or Number) Separator. Replace the semi-colon with a comma and save. Now when you export files as a CSV, they will use the comma format. Note that the exact location of this setting may differ across operating systems.


Also, check to make sure that your CSV aligns with Klaviyo’s formatting requirements. If you have not already, head to our documentation on formatting your data. For example, one of the required fields is for email addresses. This must be the first field listed in your upload with a title containing either "Email" or "Email Address."

Incorrect Date or Timestamp Formatting

You may be using the wrong format for dates or timestamps. If you have included either and are unsure of Klaviyo’s accepted formats, head to Acceptable Date and Timestamp Formats for Profile and Event Properties.

Duplicate Headings or Required Values

Check for duplicate headings or column headings with blank values. If you have multiple blank columns, delete all blank columns to the right of those with values. Otherwise, open the file in a plaintext editor and delete any extra commas that have no values in between them.

For required values (e.g., email addresses) you cannot have duplicates. Before you import a file, you can check for duplicate email address entries in Microsoft Excel by clicking Data > Remove Duplicates.


Missing Value in a Required Field

Check that all required fields have values associated with them. For example, if one of your contacts listed is missing an email address under the email column, you will see an error when uploading. Check to make sure that each contact you wish to upload has a value for all required fields. If they are empty, fill them in prior to your next attempt to upload. For information on required fields head to our article

Invalid Email Formatting

Klaviyo will automatically skip email address entries that are not in a valid format. A valid email address, such as, is made up of a local part (jane), an @ symbol, and a case-insensitive domain part ( If any of these required parts are missing, we consider the email invalid. If there are erroneous spaces in the email address, we will also consider the email invalid.

You can search your CSV for invalid emails. Highlight the list of email addresses and select Data > Filter. Then, filter out any email addresses that do not contain symbols like "@" or "." Fix or remove these invalid emails before re-attempting your import.


Mismatched Data Types

When you import a list into Klaviyo, you will arrive at a field mapping page. Here, you will match any properties to their corresponding data type in Klaviyo. For example, Email should have a String data type; whereas, if you upload a custom property for Birthday, you will want to set the data type to Date.


For more information about what the different data types entail and which to select when importing your list, head to About Data Types.

Additional Resources

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