Free CSV Tools
CSV Tools for Files Too Big for Excel
Split, merge, de-duplicate and repair CSV files of any size — from a few rows to many gigabytes. Everything runs in your browser, so your data never leaves your computer.
- No file size limit
- Never uploaded
- Free, no sign-up
CSV Tools
Pick the Job, Keep Your Data on Your Computer
Split CSV by Column Value
One file for every store, region, client or status — straight from a huge export.
Split Large CSV Files
Cut a CSV that Excel refuses to open into parts by rows, size or number of files.
Merge CSV Files
Combine hundreds of CSV files into one, lining up columns by name.
Remove Duplicate Rows from CSV
Delete repeated rows from millions of records, comparing whole rows or chosen columns.
Fix CSV Encoding & Delimiter
Repair garbled characters like é and switch semicolons to commas.
Large Sample CSV Generator
Download realistic test CSV files of any size, from 1,000 rows to 20 GB, with messy values on request.
How It Works
Built for the Files Other Tools Give Up On
Excel stops at 1,048,576 rows. Most online CSV tools either make you upload the file to their server or load all of it into your browser's memory, and both approaches fail or get expensive once a file reaches a few hundred megabytes.
Streams Instead of Loading into Memory
RowSlice reads your file a few megabytes at a time and writes results straight to your disk, so a 10 GB export needs no more memory than a 10 MB one. The only real limit is free disk space.
Your Values Stay Exactly as They Are
Rows are copied as text, never interpreted. ZIP codes like 00742 keep their zeros, 16-digit account numbers are not rounded, and product codes are not turned into dates — all things that happen when a CSV passes through Excel.
Private by Design
There is no upload step, no account, and no server that ever sees your data. That makes these tools usable for customer lists, payroll exports, and anything else your company doesn't allow you to put on someone else's website.
Correct with Messy Real-World Files
Quoted values containing commas or line breaks, semicolon- and tab-separated files, Windows-1252 and UTF-16 exports, blank lines and ragged rows are all handled, following the CSV standard (RFC 4180).
Guides
Guides for Large and Messy CSV Files
- How to Open a CSV File That Is Too Large for ExcelSix ways to work with a CSV that has millions of rows, from free tools to one line of code.
- Excel’s Row Limit: What Happens after Row 1,048,576The exact limits of Excel and Google Sheets, why data goes missing, and how to avoid losing it.
- Stop Excel Removing Leading Zeros from CSV FilesWhy ZIP codes, IDs and phone numbers lose their zeros in Excel, and four ways to keep them.
- Why Your CSV Opens in One Column in ExcelThe delimiter and regional-settings mismatch behind it, and four ways to get proper columns back.
- How to Convert a CSV to Excel without Breaking Your DataOpening a CSV and saving as .xlsx silently changes values. Here is the import route that does not.
- Stop Excel Turning Long Numbers into 4.5E+15Why card numbers, IMEIs and long IDs get rounded to 15 digits, and how to keep every digit.
FAQ
Questions About These CSV Tools
Do I need to install anything or create an account?
No. Every tool runs as a web page — open it, choose your file, and the work happens in the browser tab you already have. There is nothing to download, no extension, and no sign-up, so nothing about you or your file is stored anywhere.
Which browsers do the tools work in?
Chrome, Edge and Firefox, in their current versions — those are the three we have tested, and all three handle multi-gigabyte files. Firefox allows a site around 10 GB of disk storage, which was enough to split a 1 GB file with all 25 million rows intact. We have not tested Safari, so we make no claim about it. No plug-in or extension is needed anywhere.
Are the tools really free, and what is the catch?
They are free to use, with no account, no trial and no row cap. The site is paid for by advertising shown alongside the tools. Because your file never reaches a server, running it costs nothing beyond hosting a page — which is exactly why an upload-based competitor has to charge for large files and this does not.
Why will Excel not open my CSV file?
Almost always because it has more than 1,048,576 rows, which is the hard limit of an Excel worksheet. Excel loads the first 1,048,576 and warns that the file was not loaded completely; everything after that row is missing, and saving at that point writes the truncated version over your data. Six ways to open a CSV that is too large covers what to do instead, and why a CSV won’t open in Excel covers the other causes, from locked files to overlong values.
Will the tools change my values, the way Excel does?
No. Rows are copied through as text and never interpreted, so a ZIP code of 00742 keeps its zeros, a 16-digit account number is not rounded to 15 digits, and a product code like SEP-1 is not turned into a date. Those changes happen when a CSV passes through a spreadsheet, not here.
Can RowSlice open or create Excel (.xlsx) files?
No — these tools read and write CSV text only. They do not produce .xlsx workbooks, do not open Excel files, and are no substitute for a spreadsheet when you need to calculate, pivot or chart. What they do is prepare the CSV — right size, right delimiter, right encoding — so the import into Excel, Sheets or LibreOffice goes cleanly. See converting a CSV to Excel.
Do the tools keep working without an internet connection?
Yes, once the page has loaded. The code that reads and writes your file is already in the browser at that point, so you can disconnect and finish the job. That also means nothing can be sent anywhere while you work, which is the simplest way to prove a file stayed on your machine.
Split, Merge and Clean CSV Files of Any Size
Free, no sign-up, and your files are never uploaded.