Microsoft Excel Backup File (.xlk)
The XLK file extension stands for Microsoft Excel Backup File. It is a backup file created by Microsoft Excel to store a copy of an existing Excel file (such as XLSX or XLS) to safeguard against data loss or corruption. This feature, which dates back to earlier versions of Excel, allows users to recover their work in case the original file becomes unusable. While newer Excel versions rely more on autosaving and version history, the XLK backup remains a useful tool for data recovery and archival purposes.