Excel · .xlsx .xls
Excel · .xlsx .xlsExcel cannot open the file because the format or extension is not valid
Excel cannot open the file 'Budget 2026.xlsx' because the file format or file extension is not valid. Verify that the file has not been corrupted and that the file extension matches the format of the file.
Excel looked inside the file and did not find a workbook it could start reading. Either the file is something else with an Excel name, or the start of it is damaged.
Fix it now, free
Drop the file here. We show you what is wrong and the repaired file before you download it. Nothing is stored.
.xlsx .docx .pptx .xls .doc .ppt, up to 50 MB
Why it happens
- The ZIP container every .xlsx file is made of is damaged: its index at the end is missing because the file was cut short.
- The file was renamed: a CSV, an HTML page or an old .xls saved with a .xlsx name (or the other way round).
- An older .xls whose internal table of contents was damaged, so Excel cannot find the workbook inside it.
Try these first, they're free
- 1Open the file in a text editor. If it starts with readable text, commas or <html>, it is not a workbook: rename it to .csv or .html, or ask whoever sent it for the real file.
- 2If the file came from email or the web, right-click it, choose Properties, tick Unblock and press OK. Windows blocks downloaded files, and Excel then refuses to open them in ways that look like damage.
- 3Check the file's size. A file of 0 KB holds nothing at all: no repair can bring it back, so look for another copy (the sender, OneDrive version history, a backup).
How we fix it
We read the file by its contents, not its name. A damaged .xlsx gets its container rebuilt from the parts that survived; a damaged .xls has its internal filesystem rebuilt and comes back as a modern .xlsx.
On 384 damaged Office files, we recovered 81% of the content; Office's own repair recovered 53%. See the benchmark.