Corrupt an Excel Spreadsheet Online
Corrupt an Excel spreadsheet (.xlsx or .xls) online for free. Client-side XLSX corrupter that breaks the workbook package so Excel cannot repair it.
- No upload
- No size limit
- No sign-up
Corrupt your Excel file
Tuned for .xlsx, .xls, .xlsm, and works with every other format too.
Why Excel files are hard to corrupt properly
An .xlsx workbook is a ZIP archive of XML parts: worksheets, a shared string table, styles, relationships. Excel is unusually good at recovering from partial damage, so a handful of random flips normally produces a workbook that opens with a warning and all the data intact. To make it genuinely unreadable, the archive itself has to go.
What this tool destroys
- ZIP entry headers. Every local file header inside the package is destroyed, including
xl/workbook.xmland each worksheet part. - Central directory and EOCD. The archive index and its terminating record are overwritten, so the file no longer registers as a ZIP container.
- Relationship parts. The
_relsentries binding worksheets to the workbook are caught by the same pass. - Legacy .xls. Older BIFF workbooks are handled through their OLE compound header and FAT sector map.
What you will see afterwards
| Application | Behaviour |
|---|---|
| Microsoft Excel | "Excel cannot open the file because the file format or file extension is not valid." |
| Google Sheets | Import fails with an unsupported-file error. |
| Numbers on macOS | Refuses to import the workbook. |
| pandas / openpyxl | Raises BadZipFile, useful for testing error handling in data pipelines. |
Common reasons people do this
- Testing an ETL job that ingests spreadsheets and must not crash on bad input.
- Confirming a finance or reporting tool shows a message rather than a stack trace.
- Generating malformed workbooks for an automated test suite.
- Demonstrating why version history and backups matter during training.
How to corrupt a Excel file
- Drop your .xlsx file onto the box above, or click to browse.
- Leave the level on Standard unless you want partial damage (Light) or need to defeat recovery software (Heavy).
- Press Corrupt file. Processing happens on your device, so it finishes almost immediately.
- Download the result. It keeps the original filename and byte length by default.
Excel FAQ
Will Excel offer to recover the workbook?
It may offer, but recovery fails at Standard level and above. The container index is destroyed, so Excel cannot locate a single worksheet part to salvage.
Does it work on macro-enabled files (.xlsm)?
Yes. .xlsm uses the same package format as .xlsx and is handled identically.
What about CSV files?
CSV is plain text, so the engine switches to injecting invalid UTF-8 sequences throughout. Use the dedicated CSV corrupter for that.
Is there a file size limit?
None imposed by us. Processing runs in slices, so large workbooks are handled without exhausting memory.