Identify records imported by Data Import Wizard

In Salesforce Classic
 

1. Click Setup, go to Jobs | Bulk Data Load Jobs.
2. Click the Job ID link.
3. Click View Result.
4. Open the downloaded file via Notepad.
5. Click File.
6. Click Save As and indicate a file name with an extension of .csv
7. Open the file with an extension of .csv.
 

In Lightning Experience

1. Click the gear icon, go to Setup | Environments | Jobs | Bulk Data Load Jobs.
2. Click the Job ID link.
3. Click View Result.
4. Open the downloaded file via Notepad.
5. Click File.
6. Click Save As and indicate a file name with an extension of .csv.
7. Open the file with an extension of .csv.

Note​: The Bulk Data Load Jobs page is not available in Professional Edition, you can check the status of your upload by monitoring the relevant tabs in Salesforce.

If your organization is on Professional Edition or lower, users may manually compare the newly created records via a new list view or Edit List View Filters for an existing list by using the filter created date equal to the date of your import. Alternatively, Build a Report to manually compare the newly created records against the data contained in the import file to identify what records that may not have been imported.

Please consider promoting the Idea, Log file for Import Wizard so what we may see functionality to easily identify what records were updated, inserted or may have failed added to the Data Import Wizard with a future release.
 

See also

Import Data with the Data Import Wizard 
Open the result file from Bulk Data Load Job page