Answers.Body: <p>Assuming standard fields (First/Last name, address, email, etc.), you could export the necessary fields from Civi via a search results action (Export Contacts) and use a 3rd party tool to compare your existing data to your new data and then highlight (or remove) the duplicates.</p>
  
  <p><strong>Google Sheets</strong></p>
  
  <ul>
  <li><a href="https://chrome.google.com/webstore/detail/remove-duplicates/bckmhokpcdnhhjldhhfpebhdfipmlbog?hl=en" rel="nofollow noreferrer">The Remove Duplicates Chrome Extension</a></li>
  <li><a href="https://stackoverflow.com/questions/19843406/mark-duplicate-entries-in-google-spreadsheet">Mark Duplicate Entries in a Google Spreadsheet</a></li>
  </ul>
  
  <p><strong>OpenOffice</strong></p>
  
  <ul>
  <li><a href="https://stackoverflow.com/questions/17124237/highlight-duplicate-value-in-open-office-org-calc">Highlight Duplicate Value in Open Office Calc</a></li>
  </ul>
  
  <p><strong>Microsoft Excel</strong></p>
  
  <ul>
  <li><a href="http://www.accountingweb.com/technology/excel/identifying-duplicate-values-in-an-excel-list" rel="nofollow noreferrer">Identifying Duplicate Values in an Excel List</a></li>
  </ul>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2016-04-07T18:12:48.133Z
Answers.Text: Hmm, intriguing!  I'll look this over and mark it accepted if this works out, which I imagine it will.  Thank you!
Answers.UserDisplayName: Jon G - Megaphone Tech
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2016-04-07T19:21:52.973Z
Answers.Text: You're most welcome! When we were preparing our data for initial import, we did manually cleaning from multiple different systems so as to not clutter up Civi (and we were still learning), and we used a number of Excel functions to help.
Answers.UserDisplayName: Allen Hutchison
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2016-04-07T16:48:55.993Z
Answers.LastActivityDate: 2016-04-07T16:48:55.993Z
Answers.LastEditDate: 2017-05-23T12:38:59.763Z
Answers.UserDisplayName: Allen Hutchison
Answers.Body: <p>I like Allen's answer but it seems there should be an approach at the point of import that would work. Esp if you had a gazillion contacts in the db already. Is the issue here is that the potential matches are more complex than any matching rules?</p>
  
  <p>If there is a Matching Rule or a series of them that can work for you - then start with the loosest rule and then rerun and tighten them - and set your import to SKIP.</p>
  
  <p>Eg, if you first run the import with First Name match, then every record that has a matching first name will be reported back to you. Then run it with eg First AND Last, or First AND Phone etc.</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2016-04-22T16:12:54.427Z
Answers.Text: This is a good answer, and at first I thought I'd be accepting it!  However, I ended up doing it this way and Allen's way.  In practice, Allen's answer has the edge because it provides a means to look at both old and new contact info together on a single spreadsheet.
Answers.UserDisplayName: Jon G - Megaphone Tech
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2016-04-07T18:27:51.007Z
Answers.LastActivityDate: 2016-04-07T18:27:51.007Z
Answers.UserDisplayName: petednz - fuzion
Body: <p>I have a list of about 1000 contacts I'd like to import.  Unfortunately, there's no definitive way of linking the people on my spreadsheet to the contacts already in the database like an external identifier.  So I'd like to generate a list of potential duplicates so I can go over them by hand.</p>
  
  <p>Does anyone have a good way to accomplish this?</p>
  
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2016-04-07T15:34:40.020Z
Comments.Text: Potential duplicates within the CSV file itself (2 John Smiths are in the CSV), or potential duplicates relative to the Civi database (1 John Smith in the CSV and 1 John Smith in the database)?
Comments.UserDisplayName: Allen Hutchison
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2016-04-07T16:00:43.880Z
Comments.Text: Potential duplicates relevant to the Civi database.
Comments.UserDisplayName: Jon G - Megaphone Tech
Tags: <import><duplicate-contacts>
Title: How can I detect potential duplicates in a CSV I want to import?
ThreadText: # How can I detect potential duplicates in a CSV I want to import?
  
  (Asked by: username_0 on 2016-04-07)
  
  I have a list of about 1000 contacts I'd like to import. Unfortunately, there's no definitive way of linking the people on my spreadsheet to the contacts already in the database like an external identifier. So I'd like to generate a list of potential duplicates so I can go over them by hand.
  
  Does anyone have a good way to accomplish this?
  
  **Tags:** import, duplicate-contacts
  
  > **Comments:**
  > **username_1**: Potential duplicates within the CSV file itself (2 John Smiths are in the CSV), or potential duplicates relative to the Civi database (1 John Smith in the CSV and 1 John Smith in the database)?  
  > **username_0**: Potential duplicates relevant to the Civi database.  
  
  ---
  
  ## 2 answers
  
  ### Answer by username_1 on 2016-04-07. Score: 2 | Accepted answer
  
  Assuming standard fields (First/Last name, address, email, etc.), you could export the necessary fields from Civi via a search results action (Export Contacts) and use a 3rd party tool to compare your existing data to your new data and then highlight (or remove) the duplicates.
  
  **Google Sheets**
  
  * [The Remove Duplicates Chrome Extension](https://chrome.google.com/webstore/detail/remove-duplicates/bckmhokpcdnhhjldhhfpebhdfipmlbog?hl=en)
  * [Mark Duplicate Entries in a Google Spreadsheet](https://stackoverflow.com/questions/19843406/mark-duplicate-entries-in-google-spreadsheet)
  
  **OpenOffice**
  
  * [Highlight Duplicate Value in Open Office Calc](https://stackoverflow.com/questions/17124237/highlight-duplicate-value-in-open-office-org-calc)
  
  **Microsoft Excel**
  
  * [Identifying Duplicate Values in an Excel List](http://www.accountingweb.com/technology/excel/identifying-duplicate-values-in-an-excel-list)
  
  > **Comments:**
  > **username_0**: Hmm, intriguing!  I'll look this over and mark it accepted if this works out, which I imagine it will.  Thank you!  
  > **username_1**: You're most welcome! When we were preparing our data for initial import, we did manually cleaning from multiple different systems so as to not clutter up Civi (and we were still learning), and we used a number of Excel functions to help.  
  
  ---
  
  ### Answer by username_2 on 2016-04-07. Score: 3
  
  I like username_1's answer but it seems there should be an approach at the point of import that would work. Esp if you had a gazillion contacts in the db already. Is the issue here is that the potential matches are more complex than any matching rules?
  
  If there is a Matching Rule or a series of them that can work for you - then start with the loosest rule and then rerun and tighten them - and set your import to SKIP.
  
  Eg, if you first run the import with First Name match, then every record that has a matching first name will be reported back to you. Then run it with eg First AND Last, or First AND Phone etc.
  
  > **Comments:**
  > **username_0**: This is a good answer, and at first I thought I'd be accepting it!  However, I ended up doing it this way and username_1's way.  In practice, username_1's answer has the edge because it provides a means to look at both old and new contact info together on a single spreadsheet.  
  
  ---
  
  