Clean a CSV Online: Dedupe and Fix Columns

Drop the file above and leave Remove duplicates ticked. Exact duplicate rows are removed, and so are rows that repeat the same email (or whichever column you pick as the key), ignoring case and spaces. The first copy of each is kept.

No. The file is read, checked and cleaned in your browser, on your device. Nothing is sent to a server, so it's safe for customer lists and other personal data.

Excel often guesses the wrong text encoding for CSVs, which turns accented names and symbols like € into garbage such as é. Tick Excel-friendly before downloading: it adds a UTF-8 byte-order mark so Excel reads the file correctly. If everything lands in one column, your Excel expects a different separator; the cleaned file keeps the one your original used.

Set Duplicate when the same to your email column (it's picked automatically when one is detected). Every later row with an email you've already seen is flagged as Same key, even if the name or capitalisation differs.

It samples each column and tests the values against patterns for emails, phone numbers, dates, currency, numbers, URLs, names and IDs, with the header as a hint. The percentage next to each column is how many filled cells actually pass, so a 92% valid email column has a few broken addresses worth fixing.

Yes. Files with 50,000+ rows are read in chunks and checked in batches, so the page stays responsive. The preview shows the first 100 rows; the download includes every row.

Tick Dates to ISO and every date column is rewritten as YYYY-MM-DD, which sorts correctly and imports cleanly into databases and CRMs. It reads formats like 03/14/2025, 14.03.2025, Mar 14 2025 and 14 March 2025, and works out day-first versus month-first from the column.