Write the desired boundary in ordinary words
Before entering a pattern, name one file that should disappear from scans and one similar file that must remain. Jellyfin's non-empty .ignore uses documented pattern rules on supported versions. A pattern that hides the unwanted sample is only half a successful check.
Keep the sample reversible
For an owned video project, use copied final and temporary files in a small test directory. Record their exact relative locations and the expected outcome. Apply the narrowest rule that expresses the intention, preserve the previous marker and rescan.
If both files disappear, investigate the rule's breadth and the marker's directory scope. If neither disappears, check the marker name, version and whether the rescan reached the intended directory. Do not delete the temporary file to make the visible result look correct; that would stop testing the exclusion rule.
Save the expectation beside the policy
Keep the two sample outcomes and a plain-language reason in maintenance notes. Reuse the check when folder layouts change. The retained expectation helps another administrator distinguish an intentionally hidden project file from a finished video accidentally caught by a later rule.
Questions answered
Do scan exclusions erase the source file?
This workflow concerns discovery. Keep the original files intact and verify the library result.
Sources & further reading
Official references for the subjects discussed. Service terms and device software can change.