IFilters are plugins that are used by various indexing applications like Windows Search, the Windows indexing service, Windows Desktop Search, Exchange Server or SQL Server. An IFilter makes the contents of a filetype indexable and thus searchable. File contents cannot be indexed or searched if no IFilter plugin is available for that specific filetype.
The Windows IFilter Explorer provides an overview of all IFilter plugins that are installed on the Windows operating system. It will display the path and name of the IFilter along with the filetypes that it supports. Various software programs are listed as tabs on the top to switch to the known IFilters of these programs.
It has to be noted that IFilter Explorer has not been updated for about three years which means that some newer applications that make use if IFilters are not in the list. This does not interfere with the data that is displayed in the application window on the other hand. (for example: Windows Search 3.0 is shown in the tabs but not Windows Search 4.0).

The IFilter Explorer can be used to analyze the various IFilter plugins that are installed on the computer system. It can also be used to find filetypes that are not fully indexed by the various applications that support iFilter. The developer of the application is offering several IFilters for download on the website. It does seem that the application is not developed actively anymore.

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[...] Windows IFilter Explorer The Windows IFilter Explorer provides an overview of all IFilter plugins that are installed on the Windows operating system. It will display the path and name of the IFilter along with the filetypes that it supports. Various software programs are listed as tabs on the top to switch to the known IFilters of these programs. (tags: 1_Client 2_Freeware 3_Both 4_HelperTools 4_ITManagement 4_SharePoint IFilter) [...]