Too many columns for Excel — over the 16,384 column limit
A wide export — transposed data, a matrix, one column per date or per survey question — imports into Excel and the columns past a certain point just aren't there, or the import refuses outright. Drop the source file in below to read every column it actually has.
What this looks like
A CSV or text import throws “This workbook contains more than the maximum number of columns... some data may not have been imported,” or the import runs clean but the data ends at column XFD with no indication anything was cut. Wide, transposed, or matrix-style exports (one column per date, per sensor, per question) are the most common way to hit this without expecting it.
Why it happens
The .xlsx/.xls worksheet grid tops out at 16,384 columns (labeled A through XFD) by 1,048,576 rows. That ceiling is part of the file format itself, the same on every version and every machine — it isn't something a setting or more RAM changes, and a file can be well under any size limit and still be too wide.
What you actually want
Every column the file actually has, not just the first 16,384. xlsx-for-ai reads a file's columns directly rather than placing them on a worksheet grid, so a wide source doesn't get silently cut — you can see the true column count, pull the ones you need, or convert the file without losing anything past Excel's width.
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