CSV CLEANER + EXCEL CONVERTER

Clean rows.
Keep the details.

Remove duplicates and stray spaces. Turn a messy CSV into a clean spreadsheet—without losing leading zeros or sending your data away.

Your files stay here.

Local processing. No account.
Free CSV, TSV and Excel downloads.

01 / INPUT & SETTINGS

Start with your data

Choose a CSV or TSV fileor drop one here · up to 5 MiB

UTF-8 and UTF-16 BOM detection. Other encodings can be selected below.

Or paste your data

Quoted commas, double quotes and multiline cells are supported.

SeparatorFile encoding

First row is a header

Choose what to cleanTrim spaces at the start and end of cellsRemove blank rows including whitespace-only rowsRemove duplicate rows keep the first occurrence, in original order

Match duplicates using specific columns

Run once to see your columns. With none selected, every column must match. Matching is case-sensitive, after any selected trimming.

Your columns will appear here.

CSV and TSV export options

Guard formula-like cells Add an apostrophe before values beginning with =, +, − or @. Excel output always keeps the original text.Include a UTF-8 byte-order mark Helps Excel recognize accented characters in CSV and TSV.

Add a file or paste data to get started. Nothing is changed by default.

02 / REVIEW & DOWNLOAD

Your cleaned table

No file yet

See the changes before you save.

Your rows will appear here, with a clear count of what changed. IDs, dates and amounts stay as text.

Rows before: 0
Rows after: 0
Columns: 0

Keep every digit.

Excel stores every cell as text: 00123 stays 00123, long IDs stay intact, and formula-like values never run.

A WORKED EXAMPLE / SYNTHETIC DATA

Six rows in. Four useful rows out.

A contact export can contain a repeated record, an empty row and IDs that a spreadsheet mistakes for numbers. The built-in sample includes all three. Here is what changes—and what must not.

Before cleaning · 6 data rows

Two identical Ada records, one blank row, and three other contacts. Ada’s name has a space on each side.

00123                 |  Ada 
00456                 | Lin
00123                 |  Ada 
                      | 
00007                 | Sam
12345678901234567890  | Jo

After cleaning · 4 data rows

The first Ada record stays. One duplicate and one blank row are removed; names are trimmed. Every ID keeps its digits.

00123                 | Ada
00456                 | Lin
00007                 | Sam
12345678901234567890  | Jo

Only the ID and name columns are shown here. The sample’s email and notes columns are retained too, including a quoted comma and a multiline note.

Choose Try an example in the input panel.
Keep the header on. Enable trimming, blank-row removal and duplicate removal; leave duplicate-key columns unselected so the whole row must match.
Choose Preview & clean, then review the 6 → 4 count before downloading Excel.

Sam’s note =1+1 stays literal text in Excel; it does not become 2. CSV/TSV with the formula guard on adds an apostrophe instead. If you match duplicates by ID alone, differing notes can be discarded because the first matching record wins—review your key choice before exporting.

SMALL FIXES. NO SURPRISES.

Ready for the next import.

Clean only what you choose

Trimming, blank-row removal and duplicate removal are off until you choose them. Exact duplicate matching keeps the first row. Your source file is never overwritten.

Excel without changed IDs

CSV files have no cell types. Spreadsheet apps can guess wrong about product codes, dates and long numbers. The Excel download writes text cells explicitly. Convert selected columns to numbers in Excel when you need calculations.

Clear, practical limits

Up to 5 MiB, 50,000 data rows, 100 columns and 500,000 cells. Each cell may contain up to 32,767 characters. Outputs are limited to 40 MiB each. Invalid quotes, mismatched columns and unreadable text are explained—not silently fixed.

Why did a value gain an apostrophe in my CSV or TSV?

When the formula guard is on, values that could be interpreted as spreadsheet formulas get a leading apostrophe. This changes those text exports and reduces accidental formula execution. Behavior varies by spreadsheet app, so Excel (.xlsx) is the recommended option: it preserves the original value as a text cell with no formula. CSV and TSV do not guarantee preservation of leading zeros when opened in a spreadsheet.

Does this upload, store or train on my data?

No. Parsing, cleaning and file generation happen in this browser tab. File contents and names are not sent to FastTool. Your source and results are not saved between visits. Clear removes them from the workspace; already downloaded files remain on your device.

Clean rows. Keep the details.