Clean CSV and Excel files in your browser

Q: Is my file uploaded anywhere?

No. The page reads your file with your browser and processes it in memory. The page's security policy blocks network requests from its own code, so it cannot send your data out. You can confirm in your browser's network panel.

Q: How are duplicates found?

Either whole-row matches or matches on the key columns you choose, optionally ignoring letter case. The first occurrence is kept and a sample of removed rows is shown.

Q: Does it change my original file?

No. It never writes to your original. You download a new cleaned file.

Drop a file here, or click to choose.csv, .tsv, .txt, .json or .xlsx · up to 200 MB

or paste data

Paste CSV or tab-separated data

Choose what to fix

Cleaning

Duplicates

Remove duplicates by

Ignore letter case when matching

The first row of each group is kept. Matching runs after cleaning, so " Ann " and "Ann" count as the same.

Find and replace

Columns

Keep	Rename	Detected	Case	Numbers	Dates	Key

Numbers: strips currency symbols and thousands separators, turns (5) into -5. Dates: converts to YYYY-MM-DD; anything unreadable is left alone.

What changed

Preview of the cleaned file

Download

Protect against spreadsheet formula injectionPrefixes cells that start with =, +, - or @ (but not plain numbers) with an apostrophe so Excel will not run them.

Add a UTF-8 byte-order markHelps older Excel versions show accented characters correctly.

How it works

Open a file

Drop a CSV, TSV, JSON or .xlsx file, or paste cells. The delimiter and text encoding are detected for you.

Pick fixes

Every fix is a switch. The preview and a count of what changed update as you go, so nothing happens silently.

Download

Save CSV, TSV or JSON. Your original file is never touched.

What it can do

Duplicates

Remove whole-row duplicates or match on key columns such as email, with optional case-insensitive matching. See a sample of what was removed.

Whitespace and hidden characters

Trim and collapse spaces, replace non-breaking spaces, strip zero-width characters and control codes that break lookups.

Dates and numbers

Convert mixed date formats to YYYY-MM-DD with a day-first or month-first choice, and turn "$1,200.50" or "(75)" into plain numbers. Unclear values are left unchanged and counted.

Empty and placeholder values

Drop empty rows and columns, and blank out placeholders like N/A, null or NaN.

Headers and columns

Rename, remove or snake_case columns. Duplicate header names are made unique.

Find and replace

Plain text or regular expressions, on one column or all of them.

Column profile

For each column: detected type, unique values, empty cells and ambiguous dates.

Excel and encodings

Reads .xlsx values (choose the sheet), UTF-8, UTF-16 and Windows-1252 text, with a note when it had to guess.

Safer exports

Optional protection against spreadsheet formula injection, and an optional byte-order mark for Excel.

Repeatable settings

Save your settings as a small JSON file to document what you did.

Privacy you can check

This page has no server-side code for your data and no analytics, ads, cookies or third-party scripts. Its security policy (connect-src 'none') tells your browser to block network requests made by the page, so it cannot send your file anywhere. To verify: open your browser's developer tools, go to the Network tab, clean a file, and watch that nothing is sent. You can also turn off your internet connection after the page loads and it keeps working. Your data lives in this tab's memory until you close it or choose "Clear data".

Files are parsed as plain text and shown as text, never run as code. Downloads are created in your browser.

Limits, stated plainly

Files over 200 MB are refused. Very large files (hundreds of thousands of rows) can be slow because everything is held in memory.

.xlsx import reads values of one sheet at a time. Formulas are not recalculated, and formatting, charts and macros are ignored. Old .xls, .ods and PDF files are not supported.

The preview shows the first 100 rows; the download contains every row.

Date conversion cannot know whether 03/04/2024 means 3 April or 4 March. Choose the order that matches your data.

It does not merge files, split columns or guess misspelled duplicates (fuzzy matching) yet.

Questions

Is my file uploaded anywhere?

No. Your browser reads the file and this page processes it in memory. See "Privacy you can check" above for how to verify it.

Which file types does it open?

CSV, TSV, TXT with a delimiter, JSON arrays of objects, and .xlsx workbooks (values of one sheet at a time). Old .xls and .ods files are not supported; save them as .xlsx or CSV first.

How are duplicates found?

Either whole-row matches or matches on the key columns you tick, optionally ignoring letter case. Matching happens after cleaning. The first occurrence is kept.

Why do my accented letters look wrong?

The file probably is not UTF-8. This tool falls back to Windows-1252 and tells you. If it still looks wrong, re-save the source as UTF-8. When opening the result in older Excel, tick the byte-order mark option.

Does it change my original file?

No. You download a new file.

Is it free?

Yes. There is no account, trial or usage limit beyond your own computer's memory.