Excel repair guides

What each corruption error actually means, the free fixes worth trying first, always, and what's realistic to recover when they fail. No mockups, no scare copy: these are the same steps we'd walk a friend through.

By the error on your screen

• “Excel cannot open the file because the file format or file extension is not valid”The flat refusal at the front door: mislabeled exports, truncated archives, and the rename tricks that solve the fake cases.
• “We found unreadable content”What clicking Yes actually does, what “removed records” means, and recovering the rows Excel throws away.
• “The file cannot be opened because there are problems with the contents”Decoding the Removed Part details, and why numbers survive while text vanishes.

By situation

• The file came back broken from data recovery or a USB driveWhy undeleted files are truncated, where a better copy might hide, and what's salvageable.
• Recover a corrupted .xlsx without ExcelLibreOffice, Google Sheets and the unzip trick: every route that needs no Office license.
• Repair a corrupted Excel file onlineThe upload question nobody asks, and how in-browser repair differs.

Choosing tools, avoiding repeats

• XLSX repair tools: free vs paid, honestly comparedWhat's genuinely free, what paid adds, and the preview standard that protects you.
• Why Excel files get corruptedThe mechanics and the short list of causes, plus the habits that prevent the next one.