Online CSV cleaner — no formulas, no scripts
Clean up CSV exports from your CRM, accounting software or form tools. Remove duplicate rows, standardise inconsistent formats and review uncertain values before downloading your cleaned file.
Up to 500 rows free · no account needed · no formulas or scripts
What a typical CSV export looks like
Some combination of these shows up in almost every raw export.
- Duplicate rows from repeated exports or merged lists
- Inconsistent capitalization — "john smith" vs "John Smith" vs "JOHN SMITH"
- Extra whitespace around values, invisible until something fails to match
- Mixed date formats in the same column — 03/04/2026, 2026-04-03, April 3, 2026
- Empty cells where a required field should be
- Text encoding issues — "café" showing up as "café"
Before / after
The same file, cleaned
| Name | Signup date | Outcome | |
|---|---|---|---|
| Formats standardised | |||
| Exact duplicate removed | |||
| Missing — unchanged | Missing date flagged for review |
Illustrative output with ISO date format selected. Clear fixes are recorded. The exact duplicate is removed. Jane’s missing date stays blank because these rows provide no reliable way to recover it.
How DataMadeClean handles it
Upload, review, download
Upload your CSV
Drag and drop the file — no account needed to try it.
Automatic detection
DataMadeClean identifies column types (names, emails, dates, phone numbers) and flags likely issues before making any changes.
Review the changes
See a before/after summary — what was deduplicated, reformatted, or flagged as incomplete.
Download the clean file
Download the cleaned CSV and change report. Review flagged values before importing the file into your next system.
Your file is only ever used to clean it. An anonymous upload and its result are deleted an hour after cleaning; signed in, results follow your account's retention setting.
Built for CSV exports
- Separators: detects comma, semicolon, tab and pipe delimiters when the file provides enough evidence.
- Encoding: reads UTF-8 and supported legacy encodings, then writes cleaned CSV output in UTF-8.
- Leading zeros: preserves existing zero padding in identifiers such as customer IDs and product codes. It does not invent missing zeros.
- Uncertain values: flags findings for review when a reliable correction cannot be derived.
- File structure: cleaning cell values is different from reconstructing a damaged file. Broken quoting or inconsistent row widths may need repair before the CSV can be read.
Need help preparing an export? Follow our CSV cleaning checklist or learn how to preserve leading zeros.
Messy CSV in front of you right now?
Clean up to 500 rows free →Questions about cleaning CSV files
Can I clean a CSV file online?
Yes. You upload the file from your browser, it is cleaned on our servers, and you download the result — there is nothing to install, and no formulas or scripts to write. Files up to 500 rows are free and do not need an account.
What does DataMadeClean change in a CSV?
Stray whitespace and invisible characters, casing on personal names, email addresses lowercased, phone numbers and dates brought to one format per column, number formatting, and duplicate rows. Every change is listed individually, so nothing is altered without you being able to see exactly what it was and what it became.
Can it remove duplicate rows?
Rows are compared after the enabled cleaning steps, and rows matching across all columns are removed with the first occurrence retained. Pro checks can flag similar names sharing an email address or phone number for review. They do not automatically merge contacts or delete near-matching rows. Exact duplicate row removal is included on every plan.
Can it detect date formats automatically?
Date handling uses the selected format, evidence in the column and the selected region. When no clear format is found, the engine can fall back to the regional convention. Check day/month interpretation before using results from mixed-source files; a plausible date is not proof of the intended date.
Will it change leading zeros?
Existing zero padding is preserved in identifiers such as customer IDs and product codes. Phone numbers can still be reformatted under the selected regional rules. Missing zeros are not reconstructed in arbitrary identifiers.
How long is my file kept?
Anonymous uploads and their results are deleted an hour after cleaning. Signed in, results follow your account's retention period, seven days by default, and you can shorten it or delete a result yourself at any time. Read the privacy policy.
Can I clean a CSV without Excel?
Yes. The file is cleaned on our servers rather than by a spreadsheet on your machine, so you do not need Excel or anything like it installed, and you can clean a file you only have a copy of in your email.
Upload a CSV and review what changed.
No signup required.
Clean a file free →Get in touch if you have a question first.