List Comparator
Compare two lists to see items found only on the left, in both lists, or only on the right. Optional trimming, empty-line removal, and case-sensitive matching keep results predictable.
Compare two line-based lists and split the results into values found only on the left, values found in both lists, and values found only on the right. Matching can ignore case, trim whitespace, and skip empty lines.
How to compare two lists
- Paste one item per line into the left and right inputs.
- Choose whether matching should be case-sensitive.
- Choose whether leading and trailing whitespace should be trimmed.
- Choose whether empty lines should be ignored.
- Run the comparison and copy any of the three result groups.
How matching and duplicates are handled
Each side is converted to a map keyed by the normalized line value. Duplicate normalized entries on the same side are collapsed, and the first encountered display value is kept.
By default values are trimmed, compared case-insensitively with toLocaleLowerCase, and empty lines are ignored. The three result groups preserve the insertion order of the unique values from their respective source maps.
Privacy and limitations
Comparison happens locally in the browser and list contents are not intentionally uploaded. Matching is line-based and does not perform fuzzy similarity, stemming, natural-language equivalence, or locale-specific collation beyond JavaScript lowercase normalization.
Frequently asked questions
Are duplicates counted multiple times?
No. Duplicate values that normalize to the same key are collapsed within each input list.
Is matching case-sensitive by default?
No. Case-sensitive matching is optional and disabled by default.
Can surrounding spaces be ignored?
Yes. Trimming is enabled by default and can be turned off.
What appears in the Both column?
Unique normalized values that occur in both lists, displayed using the value retained from the left list.
Can I compare comma-separated lists?
This tool compares one item per line. Convert or split other formats into lines first.