What happens to the values I do not edit?

Nothing. Every value you did not touch is carried through exactly as written — leading zeros, long numbers, dates that look like words, quoting and line endings included.

Why not just use Excel?

Excel silently retypes things when it opens a CSV: 00123 loses its zeros, SEPT2 becomes a date, a sixteen-digit number becomes 1.23E+15 — and saving makes the damage permanent. This editor treats every value as text unless you change it yourself.

Can I add or delete rows and columns?

Yes — add or delete rows and columns, rename headings, and use find and replace. What it deliberately is not is a spreadsheet: no formulas, no formatting, no charts.

How big a file can it open?

Files well past the 1,048,576 rows where Excel stops. The grid draws only what is on screen, so scrolling stays smooth however long the file is; the practical ceiling is stated on this page once measured, not implied.

Does saving change my quoting or line endings?

No. The download reproduces the file you opened, with only your edits applied — the same quoting style and line endings, checked by our test suite rather than promised.

Is my file uploaded anywhere?

No. When you edit a CSV file here, the work happens inside this page and the browser is told to block outbound connections, so there is no upload to intercept. Watch the Network tab of your developer tools while you edit a CSV file: the only requests are for this site’s own code, and none carries your file.

Edit a CSV file — without anything else changing

Click a cell and fix it. Leading zeros, dates, and long numbers stay exactly as written, and your file never leaves your device.

Edit a CSV fileRunning on your device

Source

Your file

or drag one here · it stays on your device

Result

Add a file. It opens right here, and nothing changes unless you change it.

How this works

Open your file. Drop a CSV onto the page, or pick one.
Fix what needs fixing. Click any cell and type. Add or delete rows and columns as needed.
Download. Save the file with your edits and nothing else changed.

What it cannot do

This is an editor, not a spreadsheet: there are no formulas, no cell formatting, and no charts, and there never will be.
Very wide files with hundreds of columns edit correctly but become awkward to navigate on a small screen.
Edits live in this page until you download; closing the tab without downloading discards them, because nothing is stored anywhere.

Questions

What happens to the values I do not edit?: Nothing. Every value you did not touch is carried through exactly as written — leading zeros, long numbers, dates that look like words, quoting and line endings included.
Why not just use Excel?: Excel silently retypes things when it opens a CSV: 00123 loses its zeros, SEPT2 becomes a date, a sixteen-digit number becomes 1.23E+15 — and saving makes the damage permanent. This editor treats every value as text unless you change it yourself.
Can I add or delete rows and columns?: Yes — add or delete rows and columns, rename headings, and use find and replace. What it deliberately is not is a spreadsheet: no formulas, no formatting, no charts.
How big a file can it open?: Files well past the 1,048,576 rows where Excel stops. The grid draws only what is on screen, so scrolling stays smooth however long the file is; the practical ceiling is stated on this page once measured, not implied.
Does saving change my quoting or line endings?: No. The download reproduces the file you opened, with only your edits applied — the same quoting style and line endings, checked by our test suite rather than promised.
Is my file uploaded anywhere?: No. When you edit a CSV file here, the work happens inside this page and the browser is told to block outbound connections, so there is no upload to intercept. Watch the Network tab of your developer tools while you edit a CSV file: the only requests are for this site’s own code, and none carries your file.

Your file is processed in this page and never uploaded — the privacy page shows how to confirm that yourself.

Common problems this solves

Excel stops at 1,048,576 rows — here is how to open the rest — Excel silently drops every row past 1,048,576, and saving makes it permanent. Open, check and query the whole file in your browser — nothing uploaded.
My CSV opened as one column — Excel used semicolons — A CSV showing everything in column A was saved with semicolons by a European Excel. Why, how to tell, and how to convert it without retyping a number.
Excel removed the leading zeros — get them back and keep them — Excel turns 00412 into 412 on open; saving makes it permanent. Check whether your file still has its zeros, keep them, or put them back — in your browser.
Compare two versions of an Excel file, cell by cell — Two versions of the same workbook, and you need the differences: rows added, removed and changed, down to the cell. Two steps in your browser, no upload.
Make a Markdown table from a spreadsheet — Turn a CSV or spreadsheet export into a Markdown table with aligned columns and escaped pipes, ready to paste into GitHub or a wiki. Nothing uploaded.
Which separator and encoding does my CSV use? — Comma, semicolon, tab or pipe; UTF-8, Windows-1252 or UTF-16. How to read what a CSV really uses from its first line, and how to convert it. No upload.
Excel dates showing as numbers like 45292 — what they mean and how to convert them — A date column full of five-digit numbers is Excel counting days since 30 Dec 1899. The arithmetic, the traps, and a one-click conversion to real dates.
The file is too large to open — in Excel, Notepad, or anything else — A CSV Excel will not open, Notepad chokes on and Sheets refuses is usually only long. Read it whole, count it, keep the rows you need — on your machine.
Excel shows #### instead of the value — what it means and what is really in the cell — Number signs across a cell mean the column is too narrow, or the value became a negative date. The value is intact; here is how to see it and keep it.
CSV UTF-8 or plain CSV — which one to save from Excel, and why the accents break — Excel offers CSV and CSV UTF-8. Pick the wrong one and accents and non-Latin names come out as ? or Ã©. Which to pick, and how to repair a file.
Excel says the file format and extension don't match — what the file really is — The warning means the file is not what its name says — usually a web page of a table, or plain CSV, named .xls. How to tell, and how to get the rows out.
pandas says "Error tokenizing data. C error: Expected 5 fields, saw 7" — find the row and fix the file — read_csv stopped because a line has more fields than the heading. Find every such row, see why — an unquoted comma, a stray break — and fix the file.
Google Sheets says the file is too large to import — the ten million cell limit — Sheets refuses a file past ten million cells, and a wide file gets there before a million rows. Count what you have and drop the columns you do not need.
Excel says the file is locked for editing — who has it, how to clear it, and how to get at the data now — Excel says someone has the file open, when often it is you, a sync client or a stale lock. What the lock is, how to clear it, and how to read the data now.
The Shopify orders CSV: one row per item, blank order fields, and how to make it one row per order — Shopify writes one row per line item and fills the order columns only on the first. Fill them down and keep phones and totals as written, in your browser.
The PayPal activity CSV: gross, fee and net, currency conversions, and the rows that are not sales — The PayPal download mixes sales, fees, refunds, transfers and currency conversions. Which rows to keep, why fees are negative, and how to filter it here.
The QuickBooks report export: title lines above the heading, subtotal rows, and getting a plain table — A QuickBooks report export carries the company name above the heading and subtotal rows in the data. Strip them here and get a table any tool reads.
The Salesforce report CSV: the copyright footer, totals rows, and 15- versus 18-character IDs — A Salesforce report export ends in a copyright footer and may carry a totals row; IDs come in two lengths. Drop the footer and match IDs, in your browser.
The Google Analytics CSV: comment lines above the heading, a second table underneath, and numbers with commas — A Google Analytics download starts with # lines, ends with a second table, and writes numbers with commas and dates as 20240131. Make it one clean table.
The Amazon Seller Central report: a tab-separated .txt that Excel opens as one column — Seller Central reports arrive as tab-separated .txt files with a summary line on top. Turn one into a clean CSV that keeps every SKU and id as written.
The Xero report export: organisation and date-range lines above the headings, and totals in the rows — A Xero report export carries the organisation name and date range above the headings and total rows in the data. Strip them here for a plain table.
The bank statement CSV: day-first dates, debit and credit in two columns, newest first — Bank downloads write dates day first, split money into debit and credit columns, and list the newest line first. One query here makes a clean ledger.
Why a German CSV opens as one column — and what 1.234 means — A German export uses semicolons between fields and a decimal comma. Why 1.234 is one thousand, not one point two, and how to convert the file safely.
A Spanish CSV: semicolons, decimal commas, and identifiers that lose their zeros — Spanish exports use semicolons and a decimal comma. The quieter problem is reference numbers with leading zeros that a spreadsheet throws away on opening.
An Italian CSV: semicolons, decimal commas, and accents that arrive broken — Italian exports use semicolons and a decimal comma, and often arrive as Windows-1252, which is why città shows up as cittÃ . How to read one properly.
An American CSV abroad: the dates are the thing that breaks — An American CSV opens cleanly almost everywhere, which is the problem: its month-first dates are read as day-first by half the world, silently.
A British CSV: it looks American, and the dates are the other way round — A British CSV uses commas and a decimal point like an American one, but writes dates day first. The two look alike until a date passes the twelfth.
Import a CSV into Google Contacts: 3,000 at a time, under headings Google knows — Google Contacts takes up to 3,000 contacts per import and reads fields by their headings. Cut a bigger file into pieces and fix the headings here first.
Upload a bank CSV to QuickBooks Online: three columns and one date format — QuickBooks Online takes bank CSVs as Date, Description and Amount, or with Credit and Debit apart. Turn a bank download into that shape here, no upload.
Import customers into Shopify: one row per email, UTF-8, and tags in quotes — Shopify keeps only the last row sharing an email or phone. Choose which one survives, and fix the encoding errors behind Illegal quoting, here first.