Compare line sets locally and list unique lines on each side while deduplicating repeated input lines.
Comparison runs locally in your browser. Interactive diff uses a bounded token count to avoid locking the page on extremely large inputs.
Trim, blank-line and case rules are explicit. Unique membership, duplicate input lines and order-only differences are reported separately so a set comparison is not mistaken for a positional diff.
Set difference answers which unique values belong to one collection and not the other. It intentionally ignores ordering and may collapse duplicates. A textual diff answers a different question: which lines were inserted, deleted, or moved in sequence. Choose the operation that matches the decision before interpreting a missing or extra line as an editing change.
Case folding, trimming whitespace, Unicode normalization, or punctuation cleanup can make two visually similar lines compare equal, but those transformations can also erase meaningful differences. Decide whether ABC and abc, or a value with trailing spaces, should be considered the same in the source system. Preserve the raw lists when the exact original representation matters.
If one list contains the same line five times and the other contains it once, a set comparison may report no membership difference even though the counts differ. Use a multiset or frequency comparison when duplicate quantity matters for inventory, logs, survey responses, or transaction-like records. Set difference is appropriate only when presence versus absence is the intended meaning.
When a difference list is handed to another person or process, keep the comparison direction clear: A minus B is not the same as B minus A. Label the source lists and normalization rules. That small amount of context prevents a correct output from being applied backwards during cleanup, synchronization, access review, or data reconciliation.
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