Open a CSV larger than Excel's 1,048,576 row limit
You open a big CSV and Excel shows a warning, "This data set is too large for the Excel grid. If you save this workbook, you'll lose data that was not loaded." The sheet stops at row 1,048,576 and everything after that line is missing. If you save, the missing rows are gone from your copy.
The limit
An Excel worksheet holds at most 1,048,576 rows and 16,384 columns. This is a hard limit of the file format, not of your computer's memory. Google Sheets has a different cap: 10 million cells per spreadsheet in total, so a wide file runs out far earlier than a narrow one.
Don't save over the original. Keep the source CSV untouched and work on a copy.
Option 1: Power Query, load only what you need
Use Data ▸ From Text/CSV, then Transform Data instead of Load. In the Power Query editor you can filter rows, remove columns and group the data before it reaches the sheet, so the result fits. Power Query reads the whole file, not only the first million rows. You can also choose Load To ▸ Only Create Connection and add the data to the Data Model, which isn't subject to the worksheet row limit, then analyse it with a PivotTable.
Option 2: split the file into parts
On macOS or Linux:
split -l 1000000 big.csv part_. Only the first part has the
header row, so add it back to the others. On Windows, PowerShell can read
and write in chunks, or you can use a free splitter tool. Each part then
opens normally in Excel.
Option 3: use a tool built for large data
- DuckDB or SQLite can query a CSV with SQL and handle tens of millions of rows on a laptop.
- Python with pandas loads a CSV into memory and filters or aggregates it. For a file larger than memory, read it in chunks.
- A text editor made for large files (EmEditor, or the less command in a terminal) lets you look at the data without loading it into a grid.
Often the real need is a summary or a subset. Aggregating or filtering before it reaches Excel gives you a file that opens fast and that you can send to someone else.
What CSV Fixer does and doesn't do here
It does not split files and it does not get around the Excel limit. The free version accepts files up to 50 MB; CSV Fixer Pro removes that cap and can fix several files at once. The whole file is read into your browser's memory, so a very large one may be slow depending on your device. It's a fit for cleaning a file (spaces, empty rows, encoding, delimiter) before you choose one of the options above, not for the row-limit problem itself.
Before choosing, ask what you actually need
If you want totals, counts or a filtered subset, Power Query or SQL gets you there without ever putting the full data in a grid. If you need to browse every row by eye, a split into several files is the practical option. If the file is large because of repeated text, removing unused columns before loading often brings it under the limit. Also check whether the source system can export in smaller date ranges, which avoids the problem entirely.
If your large file also has messy encoding, stray spaces or empty rows, clean it first. Nothing is uploaded; it all runs in your browser.
Open CSV Fixer