# Clean Event and Prospect Lists Before Import | Dedupely

> Merge duplicates inside and across event, webinar and prospect lists before they reach your CRM, then find and merge anything the import still created.

- URL: https://dedupe.ly/solutions/list-imports
- Section: solutions
- Site index: https://dedupe.ly/llms.txt
- Any page: append `.md` to its URL for this plain-text form

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Solutions Clean event and prospect lists
Imports

## Import Event and Prospect Lists Without Creating Duplicates

Merge duplicates inside and across your lists before they reach the CRM, then catch anything the import still created.
[Try for free](https://v2.app.dedupe.ly/signup)[Talk to sales](https://meetings.dedupe.ly/meetings/gaby-salinas/talk-to-sales)

### What we hear from teams that import lists every month

12%
of companies have teams spend days fixing data by looking at spreadsheet rows line-by-line before using other tools.
11%
of companies had marketing campaigns or processes stalled or broken by duplicate records.
4%
of companies saw high email bounces or spam filtering from duplicate lists.
Source: Dedupely customer call research

### Why every list import adds duplicates

The same person shows up on the webinar list, the trade show scan and last quarter's prospect export. When those lists are imported one after another, each copy becomes its own record.
- **One key per row:** importers match each row on one key, like email. A person with a different email on each list, or no email at all, comes in twice.
- **Missing keys:** event lists often arrive without a website domain or CRM ID, so rows don't match the records they belong to.
- **One row, one action:** every duplicate row runs as its own update, so workflows and sequences can fire twice.
- **Different formats:** each source names its columns and formats its phone numbers its own way.

### How Dedupely compares for list imports

| Criterion | Native CRM tools | Other dedupe tools | Custom scripts | Dedupely |
| --- | --- | --- | --- | --- |
| Duplicates inside the file | Most fold rows together only when a key like email matches exactly. | Fewer clean the duplicates inside the file itself. | Possible, if someone writes and runs them. | Merges duplicate rows inside the file, on any column. |
| Duplicates across several lists | Each file is imported on its own. | Few document combining several files into one. | Possible, with custom logic for each new list. | Combines several lists into one and merges across them. |
| Matching against existing records | Most match on one key, like email, name or domain. | Several compare an import file against the CRM. | Possible, with API access. | After the import, Duplicate Searches filtered to the new records. |
| Choosing which values survive | Few let you decide which value wins, field by field. | Most offer merge rules, with varying detail. | Whatever the script is written to do. | Field-level and primary record-level Merge Rules: keep non-blank or newest values, or append multi-value fields. |
Native CRM tools as of October 2026, from the help documentation of HubSpot, Salesforce, Pipedrive, Close, Nimble and Google Contacts.

### How to import a list without adding duplicates

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Step 1 Prepare

#### How do you prepare event and prospect lists for import?

Give equivalent columns the same header in every file, and check formats against your CRM's import requirements. Keep copies of the original files before you change anything.
- Every file needs a header row. When you combine files, only columns with identical headers become one field.
- Mark columns that can hold several values, like emails, as multi-value, so merges keep every value instead of overwriting.
- Columns come in as text, so standardize dates and phone formats in the file first.
-
Step 2 Clean

#### How do you remove duplicates from a list before importing it?

Upload your lists to Dedupely as CSV files, combined into one or kept separate, then merge the duplicates and export one clean file. No CRM connection is needed.
-
Run [Duplicate Searches](https://dedupe.ly/knowledge-base/duplicate-searches)
on email, or name with company, with exact or [similar matching](https://dedupe.ly/knowledge-base/match-options).
-
Set [Merge Rules](https://dedupe.ly/knowledge-base/merge-rules)
so non-blank values win and multi-value fields are appended.
-
See how the CSV tool works on the [CSV page](https://dedupe.ly/integrations/csv). For a quick one-off, the [free CSV tools](https://dedupe.ly/tools) merge two lists and dedupe a file in the browser.
-
Step 3 Import

#### How do you import a list without duplicating existing contacts?

Map the clean file in your CRM's importer and match on email for people, domain for companies, or record ID when you have one. Test a small sample first, then import the rest.
- Check that existing records were updated rather than duplicated, and that required fields and associations came through.
- Import companies before people, so contacts attach to the right account.
-
Step 4 Catch

#### How do you find duplicates an import still created?

Connect your CRM, filter Duplicate Searches to records created by the import, and merge what slipped through. Then set it up once, so the next list is handled the same way.
-
Use [Advanced Filters](https://dedupe.ly/knowledge-base/filters)
to keep matches where one or more records were created on the import date. If the list came in over several days, enter each date and set the filter to Any. Choose "only one" to see just the new records that duplicate existing ones.
-
[Dedupely Intelligence](https://dedupe.ly/knowledge-base/dedupely-intelligence)
finds near matches, like a nickname or a second email.
-
See [Merge incoming duplicates automatically](https://dedupe.ly/solutions/auto-merge) to merge future imports on a schedule.
[31% fewer people records after merging Read the case study](https://dedupe.ly/case-studies/recruiting-pipedrive-import-duplicates)

### What makes Dedupely different

-

#### All features included in yearly subscriptions.

Merge Rules, Auto Merge and Auto Match come with every plan. Yearly subscriptions add Dedupely Intelligence in full.
-

#### Priced by records, not seats.

Unlimited users, with no per-user fees.
-

#### Every merge on record.

Preview each merge first. Merge History keeps the original records, so you can see exactly what changed.
Got a list from last week's event? No CRM connection needed.
[Upload it and find duplicates](https://v2.app.dedupe.ly/signup)

### See how Dedupely works

[Pipedrive Recruiting How an Executive Search Firm Cut Its Pipedrive People List by a Third After an Import Duplicated Nearly Everyone, with Dedupely 9,092 people matches merged Read the case study](https://dedupe.ly/case-studies/recruiting-pipedrive-import-duplicates)
[Guide Dedupe a List Before You Import It Read the guide](https://dedupe.ly/knowledge-base/dedupe-a-list-before-you-import-it)
[Guide How to Stop Duplicates From Getting Into Your CRM Read the guide](https://dedupe.ly/knowledge-base/how-to-stop-duplicates-getting-into-your-crm)

### Frequently asked questions

#### Should you clean a list before or after importing it?

Both. Clean the file first, so someone who appears on several lists with a different email or missing fields becomes one row. After the import, check the CRM for records that should have matched existing contacts but didn't.

#### Can Dedupely check a CSV against my CRM before I import it?

No. Dedupely cleans the file itself, inside one list or across several. Your CRM's importer matches the clean file against existing records on email, domain or ID, and Dedupely then finds anything that slipped through once it's in the CRM.

#### How do you dedupe a webinar or trade show list?

Upload the attendee export, combined with the registration list if you have both. Match on email first, then on name with company for people who used a different email. Merge, export one clean file and import it into your CRM.

#### What if my lists use different column names?

Rename them before you upload. When files are combined, only columns with identical headers become one field. A column called "E-mail" in one file and "Email" in another stays separate.

#### How do you keep both emails when someone signed up twice?

Mark the email column as multi-value before you merge. Merge Rules then append the second email to the surviving record instead of overwriting the first.

### Import your next list without the duplicates

[Try for free](https://v2.app.dedupe.ly/signup)[Talk to sales](https://meetings.dedupe.ly/meetings/gaby-salinas/talk-to-sales)

### Related resources

[Glossary CRM Import Read more](https://dedupe.ly/glossary/crm-import)
[Blog Clean Spreadsheets Before or After Import Read more](https://dedupe.ly/blog/clean-spreadsheets-before-uploading-or-clean-your-crm-after)
[Knowledge base Merge duplicates in spreadsheets Read more](https://dedupe.ly/knowledge-base/merge-duplicates-in-spreadsheets)

### Explore other use cases

[Clean a CSV before importing Merge one spreadsheet or several before they reach your CRM. Learn more](https://dedupe.ly/integrations/csv)
[Clean up duplicates from form fills Merge repeat sign-ups and form submissions into one record. Learn more](https://dedupe.ly/solutions/form-fills)
[Migrate to a new CRM without duplicates Dedupe before, during and after you move to a new CRM. Learn more](https://dedupe.ly/solutions/migrations)
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