Is the file corrupt if Excel says it is too large?

No. The message is about Excel running out of room to hold the grid, not about the file. The same file opens elsewhere, and the health check here will confirm every row reads cleanly.

How big a file can this site open?

The editor and the row-based tools read from disk as they go, so length is not the limit; the size classes on each tool page state what has been tested. A file in the gigabytes is best handled through the SQL console, which never holds it whole.

Can I just open it in Notepad or a text editor?

Notepad loads the entire file as one string, so it stalls on the same files Excel does. Editors built for large files exist, but they show the text as text — the editor here shows it as a table, with columns you can scroll.

Will Excel lose rows if it does manage to open the file?

Past 1,048,576 rows, yes — it drops the rest silently after a single notice, and saving makes that permanent. A file that is merely large but under that row count is kept whole; a file over it is not.

What is the fastest way to get a smaller file for Excel?

Filter to the rows you need, or take the first or last so many, and download. Both run in the page over the whole file and show the resulting count before you save anything.

Is my file uploaded anywhere?

No. A file too big for a spreadsheet is exactly the kind people hesitate to hand over, and it never is: the editor reads it from your disk a piece at a time as you scroll, inside this page.

All guides

The file is too large to open — in Excel, Notepad, or anything else

Excel loads a file into memory before it shows a single cell, so a CSV of a few hundred megabytes makes it stall, then give up, then report that the file is too large. Notepad reads the whole file the same way. The file is not broken: the program is trying to hold all of it at once, and the tools on this site do not.

Why the file will not open

A spreadsheet program builds a grid of every cell before it lets you look at one, and a grid costs far more memory than the text it came from — a 300 MB CSV can need several gigabytes as cells. When that runs out the program hangs, crashes, or shows the "too large" message, depending on how politely it fails. A text editor that reads the whole file into one string hits the same wall a little later.

None of this changes the file. It is still a plain text file with one row per line, and it can be read a piece at a time by anything built to do that.

Open it here without loading all of it

The editor on this site reads the file from disk as you scroll and draws only the rows on screen, so a file of any length opens in the time it takes to read its first screen. Every value is shown as the exact text in the file — nothing is retyped into a number or a date on the way in — and a download reproduces the file with only your edits applied.

If you only need to know what is in it, the row counter reads the whole file and reports rows, columns and blank lines without opening a grid at all, and the health check does the same while also listing what looks wrong.

Cut it down to a size the other program can take

Most of a huge export is rows nobody will read. Keep only the rows that match a value, or the first or last so many, and the result is a file Excel opens without complaint. Every one of those tools shows the row count before you download, so you know what you are handing over.

When the rows you need are scattered, or the answer is a total rather than a list, the SQL console reads the file in place and lets you write the question directly — group, filter, sum — and download the result as CSV or as an Excel workbook.

Questions

Is the file corrupt if Excel says it is too large?: No. The message is about Excel running out of room to hold the grid, not about the file. The same file opens elsewhere, and the health check here will confirm every row reads cleanly.
How big a file can this site open?: The editor and the row-based tools read from disk as they go, so length is not the limit; the size classes on each tool page state what has been tested. A file in the gigabytes is best handled through the SQL console, which never holds it whole.
Can I just open it in Notepad or a text editor?: Notepad loads the entire file as one string, so it stalls on the same files Excel does. Editors built for large files exist, but they show the text as text — the editor here shows it as a table, with columns you can scroll.
Will Excel lose rows if it does manage to open the file?: Past 1,048,576 rows, yes — it drops the rest silently after a single notice, and saving makes that permanent. A file that is merely large but under that row count is kept whole; a file over it is not.
What is the fastest way to get a smaller file for Excel?: Filter to the rows you need, or take the first or last so many, and download. Both run in the page over the whole file and show the resulting count before you save anything.
Is my file uploaded anywhere?: No. A file too big for a spreadsheet is exactly the kind people hesitate to hand over, and it never is: the editor reads it from your disk a piece at a time as you scroll, inside this page.