Sigmera.

Clean CSVs for Constant Contact imports

Constant Contact's importer is specific about the shape of the file, not just its contents. It wants one contact per row, one worksheet, a header row with a unique label on every column, and — the rule that catches most people — first and last names in separate columns rather than one combined name field. Sigmera fixes all of that in the browser before you upload anything. There is no connected app and no API access: you clean the exported spreadsheet on your own machine, then run Constant Contact's own import with a file that already matches what it expects.

How it works

  1. 1
    Start from the export, not from a connection
    Sigmera has no Constant Contact integration, no connected app, and no OAuth grant. There is nothing to authorise and nothing in your account that Sigmera can reach. The starting point is a file already on your machine — an export from another system, a registration list, or the spreadsheet somebody emailed you.
  2. 2
    The file is read in the browser tab
    Loading the file hands it to JavaScript running in your own browser. It is parsed into memory on your device and never transmitted. There is no upload step, no queue, and no server-side copy, which is why the tools keep working if your connection drops after the page has loaded.
  3. 3
    Run the passes in the order that avoids rework
    Flatten the workbook to a single-sheet CSV, split the name column, normalise the email column, then deduplicate. Deduplicating last is deliberate: matching on an email column that has already been lowercased and trimmed catches the near-duplicates that a literal comparison walks straight past.
  4. 4
    Download, then run Constant Contact's own import
    Export the finished CSV and upload it through Constant Contact's import tool as you normally would. The mapping step is where the earlier work pays off — separate name columns and unique headers mean each field lands where it belongs instead of needing correction afterwards.

Common Constant Contact clean-ups

Split one name column into the two Constant Contact wants

This is the requirement that sends most people back to the spreadsheet. Constant Contact's formatting guidance states that information has to be separated into individual columns and that first and last names cannot be combined. Almost every export disagrees: event registrations, form fills, and older CRM dumps hand you a single Name or Full Name field. Splitting it by hand means a formula, a paste-as-values, and a manual pass over every row where the order was reversed or a middle name got in the way.

  1. Open the name splitter and load the exported file
  2. Point it at the column holding the whole name
  3. Choose whether the source is written "First Last" or "Last, First", and whether you want a middle-name column
  4. Check the preview rows where a suffix or a two-word surname appears
  5. Download the CSV with first_name and last_name as separate fields
Clean the email column before the addresses are the only key you have

Constant Contact requires each contact to have either an email address or an SMS phone number with a consent date, and its formatting guidance is explicit that special characters or extra spaces in the middle of an email address have to be removed before the upload finishes. Exports pick up both routinely — a trailing space from a form field, mixed casing from a signup widget, a stray character pasted out of an email client. The address still looks right to you and still fails on the way in.

  1. Load the file into the email column cleaner
  2. Lowercase and trim the address column in one pass
  3. Review the rows it flags as malformed rather than merely untidy
  4. Fix or drop those rows, then download the result
Flatten a multi-tab workbook into the single sheet the importer reads

Constant Contact's guidance is to consolidate information spread across multiple worksheets or tabs into the first worksheet and delete the extras, and to make sure the first row of the file is not left blank — the data should sit directly under the header row. A workbook that arrives with a summary tab in front and the real list behind it will import the summary. Converting to CSV settles the question, because a CSV has exactly one sheet by definition.

  1. Open the Excel-to-CSV converter and load the workbook
  2. Pick the sheet that actually holds the contact rows
  3. Confirm the header row is the first row, with no blank line above it
  4. Download the single-sheet CSV and import that
Convert to CSV when the list is too large for the Excel limits

The file-type limits are not the same. Constant Contact documents an XLS or XLSX ceiling of 25MB and 500,000 rows, while a CSV is allowed up to 50MB and a million rows, and VCF or TXT files stop at 2MB and 40,000 rows. Its own guidance on oversized lists points at the same conclusion: for a very large list, converting to CSV is preferable to splitting the workbook into pieces. If your export is a workbook sitting near the ceiling, changing the container is less work than changing the data.

  1. Check which limit the file is actually hitting — row count or megabytes
  2. Convert the workbook to a CSV in the browser
  3. Confirm the row count survived the conversion
  4. Import the CSV instead of the .xlsx
Collapse the duplicates a stacked list always contains

The list you import is rarely one export. It is a webinar signup sheet, a filtered view from last quarter, and a spreadsheet a colleague sent, stacked into one file — which means the same person appears more than once, usually with the addresses differing only by casing or a leading space. Deduplicating is your job, not the importer's, and it is worth doing after the email column is normalised rather than before: once the addresses are lowercased and trimmed, near-duplicates that a literal match would miss collapse together properly.

  1. Normalise the email column first so casing and spacing stop hiding matches
  2. Open the duplicate remover and match on the email column
  3. Decide which copy of each match to keep
  4. Download the deduplicated file
Give every column a unique header the mapper can read

Constant Contact matches your columns to its contact fields using the header row, and its guidance is that column headings make that matching possible and that each column needs its own unique label. Two columns both called "Phone", or a blank header above a column that matters, leaves the mapping step guessing. This is a find-and-replace job on a single row, not a rewrite of the file.

  1. Open the file and look at the header row on its own
  2. Rename any duplicated or blank labels so each is unique
  3. Use find and replace on a single column when a label needs the same edit throughout
  4. Save and import

Sources

  1. 1.Format a file before importing a contact list into Constant Contact
  2. 2.Split a contact list into smaller parts before importing it into Constant Contact
  3. 3.Import tools and methods for adding contacts to an account — Constant Contact
  4. 4.Art. 28 GDPR — Processor

Frequently asked questions

Does Sigmera connect to my Constant Contact account?
No. There is no integration, no connected app, and no API key. Sigmera cleans the exported spreadsheet inside your browser, and you run Constant Contact's own import with the result. Nothing in your account is reachable from Sigmera, so nothing in it is exposed during the cleaning step.
Why does Constant Contact reject my file when the names look fine?
Because a combined name field is not what it reads. Constant Contact's formatting guidance says information must be separated into individual columns and that first and last names cannot be combined, so a single Name column has nowhere to map. Splitting it into first_name and last_name before the upload is what fixes it — the addresses and everything else in the file can be untouched and the import will still land wrong without that split.
What file formats can I import, and how big can the file be?
Constant Contact accepts VCF and TXT files as well as CSV, XLS, and XLSX spreadsheets. The size ceilings differ by type: 25MB and 500,000 rows for XLS or XLSX, 50MB and a million rows for CSV, and 2MB and 40,000 rows for VCF or TXT. If a workbook is close to its limit, converting it to CSV raises the ceiling without touching the data.
My spreadsheet has several tabs. Which one gets imported?
Constant Contact's guidance is to consolidate everything into the first worksheet and delete the extra tabs, so a summary sheet sitting in front of your real list is what gets read. Converting the workbook to a CSV removes the ambiguity, because a CSV holds one sheet and nothing else. Check while you are there that the header row is the very first row — the guidance is explicit that the first row should not be blank.
Should I deduplicate before or after cleaning the email column?
After. Duplicate matching compares values as written, so "Jane@acme.com " and "jane@acme.com" are two different strings and survive a deduplication pass untouched. Lowercase and trim the column first and the same two rows collapse into one. Running it in the other order leaves you with duplicates that look identical on screen.
Do I have to upload my contact list to clean it?
No, and that is the point. Every pass runs client-side in your browser, so a list of names, email addresses, and phone numbers stays on your device. Under the GDPR a service that receives personal data on your behalf is a processor you have to contract with and account for. There is no transfer here, so there is no processor to name.
Can I keep a phone column for SMS contacts?
Yes. Constant Contact requires each contact to have an email address or an SMS phone number with a consent date, so the phone column matters when the address is missing. Standardising that column to E.164 — a plus sign, country code, and national number with no separators — before the import keeps the formatting consistent across rows that came from different sources.

More import guides

Clean data for Zoho CRM
Deduplicate contacts, split full names, and standardise the phone column before a Zoho CRM import — cleaned in your browser, nothing uploaded.
Clean data for Google Contacts
Deduplicate contacts, fix phone and email columns, and split names before importing to Google Contacts — cleaned in your browser, so nothing is uploaded.
Clean data for Klaviyo
Deduplicate profiles, fix phone numbers to E.164, and split names before a Klaviyo CSV import — cleaned in your browser, nothing uploaded.