CSV Validator
Check headers, required fields, duplicates and field formats before import.
Check your data before importing
One file, up to 10 MiB
Column rules
Required checks empty strings; spaces stay as data. Unique compares exact strings.
| Column | Required | Unique | Format |
|---|
Source preview
First 20 records and 200 characters per cell. Full file is checked.
Record numbers include the header as row 1. Up to 1,000 issue details shown.
| Row | Column | Issue |
|---|
Choose files to begin.
Find import problems before you upload
Inspect the original values without trimming, executing formulas or rewriting the source. Rules are yours; passing does not guarantee acceptance by a specific platform.
How to use this tool
- Choose a CSV/TSV up to 10 MiB, or try the sample. Set source encoding and delimiter.
- Review headers. Select required and unique columns, and optional text, number, integer or email rules.
- Validate every record and inspect row/column issues. Download a JSON report; source files are not modified.
A practical example
Mark customer_id as required and unique. Empty cells and repeated IDs are reported with record numbers, while 00123 remains text.
Frequently asked questions
Are row numbers physical line numbers?
No. Row 1 is the header and row 2 is the first data record. A quoted multiline field still counts as one record.
What counts as empty or duplicate?
Empty means a zero-length field. Spaces are retained and do not count as empty. Unique checks compare exact case-sensitive strings, skip empty fields and report the first matching row.
Which formats can be checked?
Strict finite decimal numbers, signed integers, and a basic email syntax check. Emails are not verified for deliverability; numeric text is never converted.
Does it repair or upload data?
No. Results stay local. The JSON report includes headers and issue locations but not field values. At most 1,000 issue details are retained while total counts remain accurate.