FREE CSV TOOLS

Compare two CSV files or clean one up.

Prepare a customer list for import, or check price and inventory changes between two exports. Free, private, and ready in your browser.

Ready

Source file

Sample datacontacts-sample.csv11 rows · 5 columns · comma

Columns

Choose CSV file

Separator & encoding

Encoding Separator

Or drop a .csv file anywhere on this panel.

Clean-up steps

Trim extra spaces“ Alice ” becomes “Alice”3 cells Remove empty rowsSkip rows with no values2 rows Remove duplicate rowsKeep one copy of repeated records1 row

Duplicate matching

Match duplicates by Keep Ignore upper/lower case

Removed copies are marked with the line that is kept.

Download options

Output Protect against spreadsheet formulas

How formula protection works

Adds an apostrophe before cells that start with = + - @, tab or CR, so Excel and Sheets show them as text instead of running them. Plain numbers such as -12.5 are left alone. Turn it off when the file goes into a database or another import, so values such as +44 phone numbers stay exactly as they are.

No cells in this file start with = + - @, tab or CR.

CLEANING PREVIEW

Cleaned data

Example data · replace with your file

8rows kept

3rows removed

3cells trimmed

Removed records are left out of this view and your download.

01 / CHOOSE YOUR SOURCES

AOriginal file

Sample datainventory-september.csv5 rows · 4 columns · comma

Columns

Choose CSV file

Separator & encoding

Encoding Separator

BUpdated file

Sample datainventory-october.csv5 rows · 4 columns · comma

Columns

Choose CSV file

Separator & encoding

Encoding Separator

02 / MATCH RECORDS

File A key 1File B key 1

Match by ID, email or SKU. Use up to 3 columns. Keys must be filled and unique in both files.

Review column mapping

Only the pairs below are compared. Different column names are allowed. A column may be used once.

Comparison rules Optional

Ignore upper/lower case Ignore spaces at the start or end

Count as the same, shown as A ≡ B:

Number format 24.0 ≡ 24.00 · 1,200 ≡ 1200 · 007 ≡ 7 Empty values blank ≡ NA ≡ N/A ≡ NULL ≡ - Date format 2026-01-01 ≡ 2026/1/1 ≡ 1 Jan 2026

Dates such as 01/02/2026 are not guessed, and 12,50 is not read as a number. Key columns always match exactly.

Rows are matched by a key column, so row order does not matter. Drop a file on A or B to replace it.

COMPARISON PREVIEW

What changed?

A = original · B = updated

A inventory-september.csv vs B inventory-october.csv Sample data Change files ↓

Values show before → after. Added rows appear only in B; removed rows appear only in A. Reports protect cells that could run as spreadsheet formulas.

Lines	Status	sku	product	price	stock
A 2 · B 3	Changed · 1 cell	A-100	Canvas tote	24.00	~~120~~→96
A 4	Only in A	A-102	Linen apron	32.00	18
A 6 · B 2	Changed · 1 cell	A-104	Wool throw	~~89.00~~→79.00	7
B 6	Only in B	A-105	Cedar coasters	18.00	40

Lines

Status

sku

product

price

stock

A 2 · B 3

Changed · 1 cell

A-100

Canvas tote

24.00

~~120~~→96

A 4

Only in A

A-102

Linen apron

32.00

A 6 · B 2

Changed · 1 cell

A-104

Wool throw

~~89.00~~→79.00

B 6

Only in B

A-105

Cedar coasters

18.00

A: 5 recordsB: 5 recordsMatched by sku3 columns compared4 differences2 unchangedNot uploaded

Report

WHEN TO USE CSVLANE

Less spreadsheet checking. More certainty.

Before importing a contact list: Remove empty rows, stray spaces and duplicate records.
When a supplier sends a new price list: Match by SKU to see changed prices, added products and removed lines.
When an export opens incorrectly: Choose the right encoding or switch between commas, semicolons and tabs.

How matching works, supported formats and questions

One key or a combination. A report you can hand over.

Match up to three key columns, such as customer ID and region. Review how differently named columns pair up, then download changed, added or removed records—or a complete status report with source line numbers. Large files are processed in a local background worker with a cancel button; files never leave this browser.

Comparing supplier price lists? Once the files agree, weigh the suppliers on a weighted scorecard in Brisk Atlas.

What the workbench handles

Real-world CSV

Commas and line breaks inside quoted cells
Escaped quotes: "Sam ""Sammy"" Ito"
UTF-8 BOM from Excel exports (detected and kept on download)
Files that are not UTF-8: Windows-1252 is detected; Shift_JIS, GBK, Big5, Cyrillic, UTF-16 and more can be chosen. Downloads are UTF-8
Comma, semicolon, tab and pipe separators, in and out

Problems it points out

Short rows: filled with empty cells and marked
Rows with extra filled cells: download stops and the line is named
Unclosed quotes: the starting line is named
Duplicate or empty key values when comparing, including combined keys

Private by design

Files are read by this browser tab and never sent anywhere. The page only remembers your option choices on this device. Files up to 15 MB each; the table previews the first 400 rows and downloads include every row.

Questions

How do I remove duplicate rows from a CSV?

Open your CSV. “Remove duplicate rows” is on by default and matches the entire row; you can match by one column instead, ignore upper/lower case, and keep the first or the last copy. Each removed row is marked with the line that is kept.

How do I compare two CSV files?

Switch to “Compare two CSVs,” add the earlier file as A and the newer file as B, and pick a shared column with a unique value in each row (a filled, unique column is suggested). The table marks changed cells, rows only in A and rows only in B across columns with matching names. You can ignore differences in upper/lower case or in spaces at the start or end of a cell.

Are my files uploaded or stored?

No. Your files are read and processed in the browser. No account or upload endpoint is used. The page remembers your option choices in this browser, never file contents. Optional analytics loads only after consent and does not receive file contents. Cloudflare Web Analytics counts visits and page speed and does not receive file contents either. You can check this yourself in your browser’s Network tab: how to check. See also the privacy notice.

What file formats and limits are supported?

Use CSV or TSV files up to 15 MB each; comma, semicolon, tab and pipe separators are detected. UTF-8 and UTF-16 are read directly, a file that is not valid UTF-8 is read as Windows-1252, and you can pick Shift_JIS, GBK, Big5, Windows-1251 and other encodings; downloads are UTF-8. Short rows are padded and marked. Rows with extra filled cells or broken quoting are pointed out by line number and must be fixed before downloading.

How do I change a CSV from semicolons to commas?

Open the file in Clean a CSV. The semicolon separator is detected automatically. Choose Comma in Output and download. Cells that contain a comma are quoted, so values such as 12,50 stay in one column. Semicolon, tab and pipe output are available too, and JSON (one object per row) for code and APIs. More on changing the delimiter.

Can a downloaded CSV run formulas in Excel?

A spreadsheet may treat a cell that starts with =, +, - or @ as a formula. Protect against spreadsheet formulas is on by default and adds an apostrophe before such cells; the page shows how many cells that affects. Turn it off for a file that goes into a database or another import, so values such as +44 phone numbers or @handles are not changed. The differences report is always protected, and plain numbers like -12.5 are never changed.

Worked examples

CSV cleaning & comparison guide

Download two small CSV files, compare them by ID, and check the three expected differences before using your own data. Task notes: remove duplicate rows from a CSV and convert a semicolon CSV to commas. Tested guides: open a CSV without changing it, compare two Excel files, check a CSV for errors and all guides.