.BK2 File Extension
File TypeWindows Indexing Service Data File
This file is saved in a binary format, which requires a specific program to read its contents.
What is a BK2 file?
System file used by Microsoft Windows' Indexing Service component, which indexes file system information for searching; often created in the C:\System Volume Information\catalog.wci\ directory and stores data used for performing file system searches.
Similarly to .BK1 files, BK2 files are typically seen with the filename propstor.bk2.