CI files exist as 2 different types. Please find information about each of them below.
Type 1: Windows Content Indexer Catalog File
Windows Content Indexer Catalog File (.CI) saves index of search information. Windows uses it to display file search results. File size is large due to amount of search data. CI files located in \cata...
Windows Content Indexer Catalog File (.CI) saves index of search information. Windows uses it to display file search results. File size is large due to amount of search data. CI files located in \catalog.wci\ folders. Created by Windows Search service cisvc.exe. Service can be disabled in Windows Features.
Do not manually open or edit CI files. They are system level files. Used by Windows 2000 and later versions. Previously called Indexing Service. Turn off with Windows Features search box. Apps available to view, edit, convert CI files without installing anything. Click links to see details.
Originally released with Microsoft Windows. Used most in Japan, with Windows 10. Many users access with Google Chrome. Related to Microsoft software. Can change file associations in Open With menu. Programs listed here support CI files. Download one and double click CI file to open manually.
Windows Search
PolySpace Verifier