Why Excel cannot open large CSV files
An Excel worksheet has a hard limit of 1,048,576 rows and 16,384 columns. That comes from how the file format numbers rows, and it has not changed since Excel 2007. A CSV file has no such limit, so a large export from a database, an analytics tool or a bank can easily hold more rows than a sheet can.
Long before that limit, Excel may struggle: it loads the whole file into memory, so a file of a few hundred megabytes can freeze it or make it run out of memory, even when it has fewer than a million rows.
What actually happens to your data
When a CSV has more rows than fit, Excel loads the first 1,048,576 and shows a message that the data set is too large for the Excel grid. The rest is simply not loaded, and if you then save the workbook, the missing rows are gone from that copy. The original CSV is untouched, but it is easy to save over it by accident.
Excel also changes values on the way in: it turns numbers with leading zeros into plain numbers, reads text that looks like a date as a date, and rounds numbers of more than 15 digits.
Four ways to fix it
- Open it in the large CSV viewer, which reads the file in pieces and needs no Excel at all. You can scroll it, filter it and download just the rows you need.
- Filter or split the file into smaller ones — for example 500,000 rows each — and open the parts in Excel.
- Use Excel’s own Power Query: Data, then Get Data from Text/CSV, then Load To with “Only Create Connection” or “Add this data to the Data Model”, which can hold more rows than a sheet.
- Use a tool built for large data, such as a database or a scripting language, if you need to analyse the whole file.
Open your large CSV file now
The quickest fix is to open the file in your browser with the large CSV viewer, which is free, reads files in pieces so their size does not matter, and never uploads them. From there you can filter the rows you need, remove duplicates, split the file or convert it to Excel across several sheets.
How to use it
- Open your file in the large CSV viewer.
- Filter or split it down to the rows you need.
- Download the result and open that in Excel.
Frequently asked questions
What is the maximum number of rows in Excel?
A worksheet holds 1,048,576 rows and 16,384 columns. Data past that is not loaded when you open a CSV.
Why does Excel say my file is not loaded completely?
Because the CSV has more rows than a worksheet can hold. Excel loaded the first 1,048,576 and stopped. Saving the workbook would lose the rest, so do not overwrite your original.
Can Google Sheets open a bigger CSV?
Google Sheets has its own limit of 10 million cells in a spreadsheet, so a wide file reaches it with far fewer than a million rows.
How do I open a CSV with millions of rows?
Use a tool that reads the file in pieces, like the large CSV viewer, or load it through Power Query into the Excel data model. Do not try to open it as a normal worksheet.
Is my file uploaded anywhere?
No. The file is read in pieces by code running in your browser and is never sent to a server. The site records only an anonymous counter with the operation and rough size buckets, such as “100–500 MB” and “1M–10M rows” — never file names, column names or any data.