Import CSV Formatter for Mailchimp (Tags, Groups, Birthdays)

How to get the Mailchimp import CSV format right

Mailchimp's format guidelines for import files are strict about a few things: one Tags column, a comma and a space between groups, birthdays without a year, the whole address in one field. Exports from stores and CRMs never look like that. This tool rewrites any export into the Mailchimp import CSV format and explains every row it had to leave out.

1. Export your contacts. Use the CSV or Excel export of your store, CRM or old email tool. Excel files are fine here — the download is always CSV, which Mailchimp needs.
2. Check the matched columns. Pick every column that holds tags (they are merged) and each column that is a group category. A status column splits the file by status.
3. Match the formats of your audience. Choose the Birthday format your Birthday field uses, and the phone format of your phone field.
4. Review the problems. Role-based addresses, typos, bounced contacts, long address lines and future opt-in dates are flagged with the row number.
5. Download one file per status. Subscribed, non-subscribed and unsubscribed contacts each get their own file, because Mailchimp applies one status to a whole import.

What changes in your file

• Email Address comes first, lowercased, with one address per contact. Duplicates are merged and keep all their tags.
• Tags from every tag column end up in one cell, separated by commas, without emoji and cut at 100 characters. A tag with a comma is wrapped in double quotes, as Mailchimp asks.
• Groups written as Weekly deals, New arrivals, whatever separator your export used.
• Birthday as 10/19 or 19-10, from full dates or month-day values.
• Address in one field with two spaces between the parts and a two-letter country code: 12 Market St San Francisco CA 94103 US. The UK becomes GB.
• Empty columns removed, because blank cells erase existing data when you update contacts.

How to import the file into Mailchimp

1. Start the import. Go to Audience › Add contacts › Import contacts, choose Upload a file and click Continue.
2. Pick the file and audience. Select the CSV, choose the audience and decide whether to tick Update any existing contacts.
3. Add tags if you like. The Tag step adds the same tags to everyone in this import, on top of the Tags column.
4. Match the columns. Match each column to an audience field, or create a new one. Send Birthday to a Birthday field, not a Date field, so birthday automations work.
5. Choose the status and finish. In the Subscribe step pick the status that matches the file name, then Finalize import › Complete Import. Repeat for the other status files.

Common Mailchimp import errors

The file is not accepted

Mailchimp takes CSV or tab-delimited TXT only. An .xls workbook or a vCard is refused. The download here is always a UTF-8 CSV.

All data lands in one column

European spreadsheet programs often save with semicolons. Mailchimp needs commas, so the tool reads semicolon files and writes commas.

Mailchimp import contacts not working for some rows

Addresses with syntax errors, accents before the @ and common typos such as gamil.com are skipped by Mailchimp, and so are the role-based prefixes on Mailchimp's blocked list, like admin@ or support@. Those go to the left-out file; shared inboxes that are not on the list, like info@, stay in with a warning.

Addresses are not imported

Mailchimp drops an address with commas between the parts, a line of 45 characters or more, or the country written as UK. The tool fixes the separators and the country and flags long lines for you to shorten.

OPTIN_TIME errors

Mailchimp shows an error for opt-in times in the future and only reads OPTIN_TIME the first time a contact is imported. Future dates are left blank here, and the others are written year-first (2025-05-02), the date format Mailchimp recommends.