Mailchimp, Klaviyo and HubSpot CSV Cleanup

Three marketing platforms, three different export shapes. HowToToolkit maps each of them onto one stable schema without connecting to your account.

Covers: Mailchimp, Klaviyo, HubSpot · Last updated

How it works

You export a CSV from Mailchimp, Klaviyo or HubSpot with the platform's own export feature, open it in the matching normalizer here, and download a cleaned CSV. There is no account connection: no API key, no password, and nothing is read that you did not export yourself.

Parsing and remapping run in your browser, so the contact list stays on your device.

Why exports never match

Two exports from the same platform can differ. Depending on the view, list or export route, the same field arrives under a different header, so merging lists or moving contacts means fixing columns by hand each time.

  • Mailchimp: headers can be readable labels such as Email Address or First Name, or merge-field codes such as EMAIL and FNAME, and tag lists may use commas or semicolons.
  • Klaviyo: the list column can be called List Name or Segment, and consent values can appear as SUBSCRIBED, true, opted_in or yes depending on the export.
  • HubSpot: a contact may have a single Name property or separate First Name and Last Name, and Company Name versus Company varies with the export view.

What you get back

Each tool maps the headers it recognises onto a fixed schema. Anything else shows up in a mapping table set to ignore, and you can assign it by hand.

  • Mailchimp CSV Normalizer: Email, FirstName, LastName and Tags. Tags are split on commas or semicolons, trimmed, de-duplicated without regard to case and rejoined consistently. Email addresses are lower-cased and trimmed.
  • Klaviyo CSV Normalizer: Email, Name, List and ConsentStatus. Consent values are standardised to subscribed, unsubscribed or unknown, and unrecognised values are marked unknown rather than guessed.
  • HubSpot CSV Normalizer: Email, Name, Company and LifecycleStage. First Name and Last Name are combined into Name when no single Name column exists. Lifecycle Stage values pass through unchanged because stage names are often customised per portal.

A typical run

Export the contacts, open the matching normalizer and check the detected mapping. Fix any column it missed, then copy or download the result. If you are moving contacts to another system, spot-check a few rows in the CSV editor. If you only need a sample for testing or for a contractor, run the CSV anonymizer first.

What it does not do

These tools clean the structure of a file. They do not check that an address is deliverable, do not tell you whether you have consent to contact someone, and do not sync anything back to the platform. A mailing list is personal data, so make sure importing it into a new system is covered by your lawful basis and the original consent. Mailchimp, Klaviyo and HubSpot are trademarks of their respective owners; HowToToolkit is not affiliated with, endorsed by or sponsored by them.

Tools used in this integration

Frequently asked questions

Does HowToToolkit connect to my Mailchimp, Klaviyo or HubSpot account?
No. It works on CSV files you export yourself. It never asks for an API key, a password or any other credential.
Is my contact list uploaded?
No. Parsing and remapping happen in your browser, so the CSV stays on your device. You can confirm this with the browser's Network panel.
What happens to custom properties and merge fields?
They stay listed in the mapping table, defaulted to ignore, and you can assign each of them to a target field manually.
Are the tools free?
The three normalizers are not marked as Pro tools at the time of writing. Check each tool page for its current status.