Why did my Salesforce lead import reject rows or create duplicates?

1. Your lead CSV

A list from a spreadsheet, a trade show, a purchased list or another CRM that you are about to import as Salesforce Leads.

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Choose a file or paste the text, then click Check file.

Result

Columns and the field each one maps to

The rules, and what they leave out

• Required. Every Lead needs LastName and Company. A row missing either is rejected.
• Email is validated: one address per cell, no spaces, no mailto:, not in Name <address> form. The tool flags likely domain typos and disposable domains. Repeated emails become separate Leads unless a duplicate rule is active in your org.
• Picklists. Default Status values are Open - Not Contacted, Working - Contacted, Closed - Converted and Closed - Not Converted; Rating is Hot, Warm or Cold; default LeadSource includes Web, Phone Inquiry, Partner Referral, Purchased List and Other; Salutation is Mr., Ms., Mrs., Dr. or Prof. Orgs customise these, and Data Loader rejects a value a restricted picklist lacks.
• Numbers. AnnualRevenue is digits and a decimal point; NumberOfEmployees is a whole number. Currency symbols, commas, ranges and suffixes such as M are rejected.
• Lengths from memory: LastName 80, FirstName 40, Company 255, Title 128, City 40, PostalCode 20, Description 32,000.
• Dates in one column should use one order. The wizard reads them in the importing user's locale; Data Loader wants yyyy-MM-dd. YYYY-MM-DD works for both.
• IDs. OwnerId must be a 15 or 18 character user ID starting 005 for Data Loader. Excel can damage IDs into scientific notation.
• Limits from memory: the Data Import Wizard takes about 50,000 records per import; Data Loader takes far more.
• Safe fixes change only the delimiter, header capitalisation, spaces, capitals and mailto: on emails, Status and Rating capitalisation, a date column that has exactly one possible reading (rewritten as YYYY-MM-DD), and a row that is an exact copy of the row above it. It never edits a name, company, phone, address, title, owner, ID or custom field.
• Not checked: your validation rules, required custom fields, duplicate and matching rules, record types, whether an address receives mail, consent, and anything Salesforce changes in its importers. Import a small sample into a sandbox first.

Common questions

Why did my Salesforce lead import reject rows or create duplicates?

The usual causes are a missing LastName or Company, which Salesforce requires on every Lead; an email that fails validation or holds two addresses; a Status value your org does not have; AnnualRevenue written as $1.2M or NumberOfEmployees as 11-50; dates in the wrong order; and no active duplicate rule, so repeated emails each become a new Lead. This tool tests each of them and names the line.

Which fields are required to import Leads into Salesforce?

From memory of the public Salesforce documentation: LastName and Company are required on a Lead, and Status takes a default value if you leave it blank. Your org may add validation rules or required custom fields, which this tool cannot see.

How do I check a lead list before importing it into Salesforce?

Paste the file or drop it onto this page. It reads the header, maps each column to the Lead field the import will probably choose, checks every row, and lists problems with line numbers grouped as errors, warnings and notes. Nothing is uploaded.

What does Apply safe fixes change?

Only things with one reasonable reading: the delimiter, header capitalisation, spaces, capitals and mailto: on emails, Status and Rating capitals, a date column where every value can only be read one way, and a row that is an exact copy of the row above. It never edits a name, company, phone, address, title, owner, ID or custom field.

Is it safe to put my lead list into a web page?

The page runs in your browser, the file is read locally and nothing is uploaded; a test in the code asserts there are no network calls. Lead lists are personal data, so keep that in mind before using any tool that uploads them.

What does this not check?

Your validation and duplicate rules, required custom fields, whether an address receives mail, whether you have consent to contact the people in it, and whether Salesforce will accept the file today. A clean result is not a promise of success.