Format Guidelines for Your Import File

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Before you import a file of contacts to MailChimp, review the format of each column in your file. During the import process, you'll match each column in your file to a column in your MailChimp list, which we call a list field. Certain list fields, like email address or birthday, require a specific format in your import file.

In this article, you'll learn how to format each column in your file to get the best results when you import.

Before You Start

  • The only field that MailChimp requires is Email Address. Any other fields you want to include are useful for personalizing campaigns, but optional.
  • You can arrange the columns in your file in any order.
  • If you’ve already started an import, learn how to review and edit your list fields or troubleshoot your import.

Required Field

Email Address

Your import file must include a column for email address, and can provide only one email for each subscriber. Email fields do not support special characters before the @ symbol, or spaces anywhere in the address. 

Optional Basic Fields

Use these common list field types to quickly add extra information to your subscriber list.


Text fields are limited to a maximum of 255 bytes of information, and will be clipped if there’s too much. In many alphabets, this is equal to 255 characters. Some alphabets or symbolic characters, like emoji, use more than one byte of information per character, so it isn't always a one-to-one ratio.

Use text fields for:

  • first name and last name
  • subscriber language preferences
  • international postal codes
  • website URLs for campaign links
  • numbers without comma separators
  • additional data you want to add to your list, like job title or company name

Zip Code

Zip code fields can only contain five digits.


International post codes aren’t supported by this field type. To store international postal codes, use a text field. If you have subscribers in many locations including the U.S., use both a zip code field and a text field.


Use a number field to import numbers or currency values to your list. We'll add comma separators to large numbers like 1,000 or 1,000,000.


To import dates other than birthdays, use either of these two formats.

YYYY-MM-DD (ISO Standard)

In the examples, MM is month, DD is day, and YYYY is a four-digit year. MailChimp will attempt to convert the date field to match your account's default date format. For best results, we recommend that you use the ISO standard format, YYYY-MM-DD.


Format U.S. phone numbers with dashes only. Avoid spaces, parentheses, and dots.


International numbers typically don't fit this format. If you have international subscribers, choose the international phone number option when you create a phone number field in your list settings.

Additional Optional Fields

Use these additional field types to add more complex information to your list. Formatting these field types can be tricky, so be sure your import file's columns match the exact format of these examples.


Mailing addresses must appear in a single cell and should include the country. If the address information in your list import is stored in multiple columns, you'll need to combine your address fields first.

To format an address cell, separate each line of the address with two spaces, as shown in this example.

1701 Bristol Ave.  Barrington   Rhode Island   02806  USA

address format screenshot


To send an automatic birthday or annually recurring message to your subscribers, use a birthday field instead of a regular date field. Be sure to use the format, Month/Day.


birthday format list


Image fields in your import file must contain the full source URL for a hosted image, which can be used to insert custom, dynamic images in campaigns.


Website fields can be used to store custom links for each subscriber. Use merge tags to insert these custom links into your campaign. To display the custom URL your campiagn, use a website field. If you want to hyperlink the custom URL to descriptive text or an image in your campaign, use a text field instead. Website fields must include the full URL of a website, including http://.

website example


If you plan to use groups in your list, you can add subscribers to groups during the import process. The group column must be formatted as shown in the example or you may encounter errors with your import.

In your file, label the group column to match your group title. For each subscriber, include their group names. To add a subscriber to more than one group name, separate each name with a comma and a space.

For example, if you have a Newsletter Preferences group title and the group names are Student Events, News, and Donations, format the Preferences cell for someone in all three groups as shown.

Student Events, News, Donations

Format list fields for groups

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