HubSpot import: "Duplicate unique property value"
HubSpot's own troubleshooting guide names “Duplicate unique property value” as an import error, raised when two or more rows in the same file share the same value in a property HubSpot treats as unique — Email for contacts, Company domain name for companies. HubSpot does compare the rows of your file against each other, and it names the collision. What it does not do is let you choose: in HubSpot's own words, “if this property is not unique in your file, only one row referenced by this property was imported” — HubSpot picks which row that is, and the other row's values do not arrive.
Built for anyone preparing a contact or company file for HubSpot or Salesforce — sales operations, RevOps, and agencies migrating a client's data.
Read from HubSpot's own Knowledge BaseHubSpot Knowledge Base — knowledge.hubspot.com, read 19 September 2026.
What this error means
HubSpot enforces uniqueness on a small set of properties — Email for a contact, Company domain name for a company, Record ID for either. When an import file carries the same value twice in one of those columns, HubSpot compares the rows against each other and raises this error: the values “were not unique when compared to other rows in your file or other records in your CRM”. Only one of the colliding rows is imported, HubSpot decides which, and the other row's values do not arrive. Three sibling errors behave the same way — Duplicate record ID and Duplicate alternate ID, both for an ID “used multiple times within your files”, and Duplicate row content for a record repeated whole. You read about any of them afterwards, in the error report, once the import has already run.
What causes it, and what our engine actually checks
CRM Import Check's duplicateKey rule reads every column mapped to a property HubSpot marks unique, normalizes each value (trimmed, lower-cased — the same comparison HubSpot's own importer applies to Email), and flags every row that shares a value with an earlier one. Run against a three-row sample file built to exercise it, the engine found the same collision HubSpot's importer would resolve on its own once the import had run — and it names which rows collide, on which property, and how their values differ, so the choice of which record survives is made here rather than by the importer.
What the engine found in a sample file
Two rows in the sample carried the same email address — one in its original case, one with a capitalized letter — and the engine flagged both as duplicateKey, a blocker. The same two rows also matched on name and company, which is what likelyDuplicatePerson is for: a second, independent signal that these are the same contact even where the unique key did not obviously collide. The capitalized copy also raised emailUppercase, a notice, since HubSpot's own comparison folds case but a CRM should still store the address the way a mail client would send to it.
duplicateKeyBlocker1 and 2“jane.doe@acmestrategies.com”
emailUppercaseNotice2“Jane.Doe@acmestrategies.com” → “jane.doe@acmestrategies.com”
likelyDuplicatePersonWarning1 and 2Blocker stops the import outright, or lets it through with data silently lost. Warning usually gets through but is worth checking before you trust the numbers. Notice is informational — safe to leave, safe to clear.
Reproduced from a sample file — read September 19, 2026.
Check your own file for this
Drop the contact file you were about to import into HubSpot below. It is read in this browser tab, the same engine runs the same check, and you will see immediately whether it carries a duplicate unique-property value.
CSV, TSV or Excel, up to 20 MB
How to fix it by hand
Sort the file by the column HubSpot treats as unique for the object you're importing — Email for contacts, Company domain name for companies — so duplicates sit next to each other. For each pair, decide which row carries the correct, most current values, and delete the other. Where the two rows disagree on a field and neither is obviously wrong, merge the answer by hand rather than guessing.
Frequently asked questions
- What does HubSpot’s "Duplicate unique property value" error mean?
- HubSpot found two or more rows in your import file that share the same value in a property it treats as unique — usually Email. It does not reject the import: only one of the colliding rows is imported, HubSpot decides which, and the other row's values do not arrive. The error report tells you afterwards, once the import has run.
- Why does CRM Import Check treat a duplicate key as a blocker rather than a warning?
- Because the outcome is a row that never arrives, and which row that is was not your decision. HubSpot does report the collision — but only after the import. A blocker is CRM Import Check's way of putting the same decision in front of you first, while both rows are still intact and you can say which one is right.
- Can CRM Import Check fix a duplicate automatically?
- No — it groups the colliding rows and shows what each one carries, but which record survives and which values are correct is a decision only a person reviewing the actual contact can make.
What CRM Import Check does with this file
Drop a file carrying this problem into CRM Import Check and it groups every colliding row by the value they share, shows both rows side by side, and lets you choose which one survives before anything is exported. It never merges automatically — which record is correct is a business decision, not a rule.
The file you'd check is read in your browser tab — it is never uploaded anywhere.
What it cannot do here
The tool finds duplicates within the file you drop. It does not check the file against contacts already inside your HubSpot portal, because that would require connecting to your CRM — which this product deliberately never does.