The access the specified extensions list to define the content X1 will index by:
1. Tools> X1 Options
2. Files > More Indexing Options button
3. File Indexing Options>Specify File Types
4. Files not in the list will still be indexed for attributes (like the file name, date, path, etc.). Files in the list will be indexed for attributes and content.
For example: if you searched for "We the People" (in the main X1 search field), you may get results in X1 like:
We like the people.mp3
The US Constitution.doc file appears because "We the People" is found in the document's contents and X1 has been set to index .doc files for content.
The "We like the people.mp3" file appears even though ".MP3" is not set to be indexed for content. This is because the search terms "We the People" appear in the file's attributes (in this case, the file name).
If you would like X1 to exclude files that have not been indexed for content from the results list, type the word "Indexed" in the "Flags" column header field (at the top of the results list). This will force X1 to only show files that have been indexed for content.