Sigmera.

Clean CSVs for HubSpot imports

HubSpot imports fail for predictable reasons: duplicate contacts, phone numbers it cannot parse, and a single name column that does not map to its First name and Last name fields. Sigmera cleans the export in your browser before you import it, so HubSpot accepts every row on the first try — and your contact list never leaves your device. The four clean-ups below cover the vast majority of failed HubSpot imports, and each one takes a couple of minutes in a browser tab with no install and no account required to try.

How it works

  1. 1
    Export from HubSpot or your source
    Export the list you want to work with as a CSV — from HubSpot itself, another CRM, a form tool, or a spreadsheet. Sigmera never connects to your HubSpot account; you work with the exported file.
  2. 2
    Clean it in your browser
    Open the file in the relevant Sigmera tools to remove duplicates, standardize phone numbers and emails, and reshape name columns. Every step runs client-side, so the file is never uploaded to a server.
  3. 3
    Import the clean file into HubSpot
    Download the cleaned CSV and run HubSpot's standard import, mapping each column to the matching property and choosing whether to create or update records. Because the file is already deduplicated and correctly formatted, HubSpot accepts the rows without rejects, without malformed phone numbers, and without creating duplicate contacts you would have to merge later. Keep the cleaned file as a record of exactly what you imported, so the next list starts from a known-good template.

Common HubSpot clean-ups

Deduplicate contacts before import

Your export from a form tool, an event sign-up, or a past list has the same person more than once. HubSpot matches on email, so duplicates either create extra contacts or collide and drop data. Remove them first, keeping the most recent row.

  1. Open the CSV in the remove-duplicates tool
  2. Choose the email column as the match key
  3. Keep the last occurrence and download the deduplicated file
Fix phone numbers to a format HubSpot accepts

Phone numbers come in every human format. HubSpot and its calling and SMS integrations expect the E.164 standard. Standardize the whole column so numbers are usable, not just stored.

  1. Open the phone column in the phone-number cleaner
  2. Set the default country for local numbers
  3. Export the column rewritten to E.164
Normalize the email column

Stray capitals and trailing spaces make the same address look like three different ones to HubSpot's duplicate check. Lowercase, trim, and validate the email column so matching works.

  1. Open the email column in the email cleaner
  2. Trim whitespace, lowercase, and drop invalid addresses
  3. Download the cleaned column
Split a full-name column into first and last name

Your file has one Full Name column, but HubSpot stores First name and Last name separately. Split it so personalization tokens work and greetings are not blank.

  1. Open the name column in the split-names tool
  2. Map the output to First name and Last name
  3. Download the reshaped file

Sources

  1. 1.Set up your import file — HubSpot Knowledge Base

Frequently asked questions

Does Sigmera connect to my HubSpot account?
No. Sigmera never connects to HubSpot or asks for API access. You export a CSV from HubSpot or your source, clean it in your browser with Sigmera, then run HubSpot's normal import. The cleaning happens entirely on your device.
What phone number format does HubSpot want?
HubSpot and its calling and SMS integrations expect the E.164 international format — a plus sign, country code, and national number with no spaces or punctuation, such as +14155550142. Sigmera's phone cleaner rewrites a whole column to E.164 at once.
How does HubSpot decide if a contact is a duplicate?
HubSpot primarily matches contacts on email address. If your file has two rows with the same email, importing can create conflicts or merge in ways you did not intend, so it is safest to deduplicate on email before importing.
Is my contact list uploaded anywhere when I clean it?
No. Sigmera processes the file with client-side code in your browser, so the spreadsheet never leaves your device. That keeps your contacts private and avoids sending personal data to a third-party server before it even reaches HubSpot.
Why not just clean the data inside HubSpot after importing?
Once rows are in HubSpot they can trigger workflows, get assigned to owners, and collect activity, so fixing them later means unwinding all of that. Cleaning the CSV before import keeps the bad rows out of the system in the first place, which is faster and far less error-prone than merging duplicate records after they have already spread across your reports and sequences.