Sixteen real workbooks, measured
Each one was attached by a real person to a public bug report about size or slowness. None is a sample dataset or a generated fixture. Every row links to the thread it came from, so you can download the same file and check.
Run on September 19, 2026 with the default set of reductions, and again with every reduction on.2 of the 16 came back under one per cent smaller, and those rows are still here. Six were written by an export library rather than by Excel: the excelize, ClosedXML, NPOI and ImportExcel rows.
| Workbook | What was taking the space | Size | Default | All on |
|---|---|---|---|---|
| excelize stream-writer exportqax-os/excelize #1142 | A package written without compression | 48.7 MB | 96.6% | 96.6% |
| ClosedXML 50,000-row reportClosedXML #1838 | 50,000 rows by 245 columns, styled cell by cell | 34.5 MB | 3.0% | 3.0% |
| Airports datasetLibreOffice #117366 | Millions of styled blank cells past the data | 26.1 MB | 71.8% | 71.8% |
| NPOI large exportnissl-lab/npoi #560 | Real data. No output, original untouched | 25.8 MB | 0.0% | 0.0% |
| 500,000-row sheetONLYOFFICE DocumentServer #116 | Worksheet data, then the calculation cache | 11.1 MB | 36.5% | 36.5% |
| ClosedXML border reproClosedXML #2517 | One border written on every cell of a column | 10.4 MB | 99.9% | 99.9% |
| Temperatures workbookONLYOFFICE DocumentServer #3315 | Worksheet data beside a heavy chart layer | 9.2 MB | 27.6% | 27.6% |
| ImportExcel 1,700-column mergedfinke/ImportExcel #506 | A column-heavy worksheet | 7 MB | 23.3% | 23.3% |
| Search performance testONLYOFFICE DesktopEditors #2451 | Shared strings holding real text | 4.7 MB | 0.4% | 0.4% |
| 17-pivot workbookLibreOffice #90129 | Seventeen pivot tables, each with its own source copy | 3.1 MB | 36.0% | 57.0% |
| Univer import crashdream-num/univer #4100 | Worksheet data, then the calculation cache | 2.4 MB | 29.5% | 29.7% |
| Huge drawing layerLibreOffice #105036 | Invisible shapes left in the drawing parts | 626.7 KB | 89.5% | 89.5% |
| 1,784 conditional formatsLibreOffice #81765 | Fragmented conditional formatting and images | 425.3 KB | 3.0% | 3.0% |
| Formula range bloatClosedXML #457 | A formula range written out cell by cell | 378 KB | 2.4% | 2.4% |
| 15,612 invisible rectanglesLibreOffice #126185 | Invisible shapes left in the drawing parts | 89.4 KB | 91.5% | 91.5% |
| 1,500 cell commentsLibreOffice #119636 | Comment anchors, kept on purpose | 61.5 KB | 18.8% | 18.8% |
Together they weighed 184.6 MB, and the default set took 47.6% off that. Drop your own file and see what it says about yours.