List comparison

About this tool

Compare two lists of identifiers, labels or task names without treating their contents as numbers. Each physical line is one item. The tool reports the intersection, A minus B, B minus A, union and symmetric difference. Comparison keys can optionally trim outer whitespace or ignore case using JavaScript lowercase rules. The displayed record keeps the first original spelling and source line, so a matching key does not silently rewrite the exported value. All processing stays in your browser; a match is a string comparison and does not establish a person’s identity, account ownership or real-world equivalence.

Executable examples: ASCII JSON requests and expected original items

{"a":"red\nblue","b":"blue\ngreen","options":{"trim":false,"caseSensitive":true}}

{"intersection":["blue"],"aOnly":["red"],"bOnly":["green"],"union":["red","blue","green"],"symmetricDifference":["red","green"]}

{"a":"b\na\nb\na","b":"a\na\nc","options":{"trim":false,"caseSensitive":true}}

{"intersection":["a"],"aOnly":["b"],"bOnly":["c"],"union":["b","a","c"],"symmetricDifference":["b","c"]}

{"a":"  Ada \nAda","b":"Ada\n Bob ","options":{"trim":true,"caseSensitive":true}}

{"intersection":["  Ada "],"aOnly":[],"bOnly":[" Bob "],"union":["  Ada "," Bob "],"symmetricDifference":[" Bob "]}

{"a":"Ada","b":"ada","options":{"trim":false,"caseSensitive":true}}

{"intersection":[],"aOnly":["Ada"],"bOnly":["ada"],"union":["Ada","ada"],"symmetricDifference":["Ada","ada"]}

{"a":"Ada\nADA","b":"ada\nBOB","options":{"trim":false,"caseSensitive":false}}

{"intersection":["Ada"],"aOnly":[],"bOnly":["BOB"],"union":["Ada","BOB"],"symmetricDifference":["BOB"]}

{"a":"\u00df\nSS","b":"ss","options":{"trim":false,"caseSensitive":false}}

{"intersection":["SS"],"aOnly":["\u00df"],"bOnly":[],"union":["\u00df","SS"],"symmetricDifference":["\u00df"]}

{"a":"\u03a3\n\u039f\u03a3","b":"\u03c3\n\u03bf\u03c3","options":{"trim":false,"caseSensitive":false}}

{"intersection":["\u03a3"],"aOnly":["\u039f\u03a3"],"bOnly":["\u03bf\u03c3"],"union":["\u03a3","\u039f\u03a3","\u03bf\u03c3"],"symmetricDifference":["\u039f\u03a3","\u03bf\u03c3"]}

{"a":"I\n\u0130\n\u0131","b":"i\ni\u0307","options":{"trim":false,"caseSensitive":false}}

{"intersection":["I","\u0130"],"aOnly":["\u0131"],"bOnly":[],"union":["I","\u0130","\u0131"],"symmetricDifference":["\u0131"]}

{"a":"\u00e9","b":"e\u0301","options":{"trim":false,"caseSensitive":true}}

{"intersection":[],"aOnly":["\u00e9"],"bOnly":["e\u0301"],"union":["\u00e9","e\u0301"],"symmetricDifference":["\u00e9","e\u0301"]}

{"a":"001\n1\n9007199254740993\n__proto__","b":"1\n9007199254740992\nconstructor","options":{"trim":false,"caseSensitive":true}}

{"intersection":["1"],"aOnly":["001","9007199254740993","__proto__"],"bOnly":["9007199254740992","constructor"],"union":["001","1","9007199254740993","__proto__","9007199254740992","constructor"],"symmetricDifference":["001","9007199254740993","__proto__","9007199254740992","constructor"]}

{"a":"\n \n\t\n","b":"","options":{"trim":false,"caseSensitive":true}}

{"intersection":[],"aOnly":[" ","\t"],"bOnly":[],"union":[" ","\t"],"symmetricDifference":[" ","\t"]}

{"a":"\n \n\t\n","b":"","options":{"trim":true,"caseSensitive":true}}

{"intersection":[],"aOnly":[],"bOnly":[],"union":[],"symmetricDifference":[]}

{"a":"a\r\nb\rc\n","b":"c\na","options":{"trim":false,"caseSensitive":true}}

{"intersection":["a","c"],"aOnly":["b"],"bOnly":[],"union":["a","b","c"],"symmetricDifference":["b"]}

{"a":"\ufeffx\n\u0085x","b":"x","options":{"trim":true,"caseSensitive":true}}

{"intersection":["\ufeffx"],"aOnly":["\u0085x"],"bOnly":[],"union":["\ufeffx","\u0085x"],"symmetricDifference":["\u0085x"]}

{"a":"\u00a0x\u00a0\nx\u00a0y","b":"x\nx y","options":{"trim":true,"caseSensitive":true}}

{"intersection":["\u00a0x\u00a0"],"aOnly":["x\u00a0y"],"bOnly":["x y"],"union":["\u00a0x\u00a0","x\u00a0y","x y"],"symmetricDifference":["x\u00a0y","x y"]}

{"a":"a\u2028b","b":"a\nb","options":{"trim":false,"caseSensitive":true}}

{"intersection":[],"aOnly":["a\u2028b"],"bOnly":["a","b"],"union":["a\u2028b","a","b"],"symmetricDifference":["a\u2028b","a","b"]}

{"a":"<img src=x onerror=alert(1)>\n=1+1\n\u202eabc\n\u0000","b":"=1+1","options":{"trim":false,"caseSensitive":true}}

{"intersection":["=1+1"],"aOnly":["<img src=x onerror=alert(1)>","\u202eabc","\u0000"],"bOnly":[],"union":["<img src=x onerror=alert(1)>","=1+1","\u202eabc","\u0000"],"symmetricDifference":["<img src=x onerror=alert(1)>","\u202eabc","\u0000"]}

{"a":"\ud800","b":"\ud800\nx","options":{"trim":false,"caseSensitive":true}}

{"intersection":["\ud800"],"aOnly":[],"bOnly":["x"],"union":["\ud800","x"],"symmetricDifference":["x"]}

Common mistakes

• Treating duplicate occurrences as repeated set members instead of one key with occurrence counts.
• Assuming case-insensitive means Unicode case folding, Turkish-specific casing or accent removal.
• Confusing escaped display text with the original values carried by TXT or JSON.
• Expecting TXT to preserve original line separators, duplicate rows, ignored lines or source metadata.
• Sharing the JSON report thinking it contains only the selected result, when it also includes both complete input lists.

Limits and notes

• —Exact trim set: U+0009, U+000A, U+000B, U+000C, U+000D, U+0020, U+00A0, U+1680, U+2000–U+200A, U+2028, U+2029, U+202F, U+205F, U+3000, U+FEFF. This is ECMAScript String.trim whitespace, not the Unicode White_Space property: U+FEFF is included, U+0085 and U+200B are excluded. CR and LF are consumed as list separators before trimming. Only outer whitespace affects the key; original spelling is retained. Case-insensitive mode uses the host’s locale-independent ECMAScript String.prototype.toLowerCase, not Unicode case folding or locale-aware collation. Greek Σ can become σ or final ς by context; ß does not equal ss. Turkish İ lowercases to i plus combining dot. No NFC, NFD, NFKC, NFKD, accent removal, width conversion, fuzzy matching or identity inference is performed.
• —Each side is limited to 131,072 UTF-16 units and 10,000 physical split lines; an empty input counts as one ignored line, and a trailing separator adds another ignored line. Files must be strict UTF-8 and at most 524,288 bytes; invalid bytes are rejected, not replaced. The file BOM is preserved, and only the trim option removes U+FEFF from a comparison key. Browser paste or clipboard behavior may alter line endings before or after this tool. The result is bounded to 20,000 unique entries and 60,000 references across the five sets. The interface shows at most 300 rows and 256 UTF-16 units per displayed cell, with a notice for clipping. TXT is limited to 1,048,576 UTF-8 bytes; ASCII JSON to 8,000,000 bytes. An exceeded limit blocks the export rather than silently shortening it. Changing input or comparison options invalidates previous results.
• —Empty comparison keys are ignored. Extra duplicates equal nonempty occurrences minus unique keys, separately for A and B. Each key keeps its first original and one-based source line. A represents shared keys; A-based results follow A order and B-only records follow B order. Union and symmetric difference append B-only entries after A entries. No numeric conversion, sorting or duplicate frequency expansion is applied.
• —TXT joins selected original items with LF and adds no final LF. It preserves raw controls, bidi characters, HTML-like text and spreadsheet formula prefixes, with no CSV or formula protection. Unpaired UTF-16 surrogates block raw TXT copying and downloading to prevent replacement loss. Review the destination; a safe ASCII preview does not make raw text safe for another application.
• —JSON losslessly preserves both full original inputs, including ignored rows, duplicate spellings and original CRLF/CR/LF separators, together with options, statistics and all five sets. It escapes non-ASCII, controls and unpaired surrogates. It contains more than the selected set and is not anonymization or encryption. Inputs are not uploaded, remotely queried or persisted by this tool; copying or saving is an explicit user action.

Frequently asked questions

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