What is finding unique items?

'Which items appear exactly once?' is a more useful question than it first appears. A list of order IDs where you want the ones that were never duplicated. A column of serial numbers where duplicates indicate a data-entry error. A merge of two contact lists where the items appearing once are precisely the ones that did not overlap. This tool filters your list down to the items that occur only once, discarding everything that repeats.

The options exist because real lists are messy. Split the input by a symbol or a regular expression. Turn on trimming so ' apple ' and 'apple' count as the same item instead of two. Case-insensitive matching treats 'ID-100' and 'id-100' as duplicates of each other. You can choose the output separator and drop empty items left behind by trailing commas. There is also a dedupe mode for the opposite question: collapsing repeats so each distinct item is kept once, when what you want is the set of values rather than the once-only items.

The distinction matters, so to be concrete: from the input a, b, a, c, b, d, unique mode returns c and d (the items seen exactly once), while dedupe mode returns a, b, c, d (each distinct item once).

Processing happens locally in your browser as you type, with nothing sent to a server — safe for customer lists, credential inventories, or anything internal. For large lists it stays instant, since counting occurrences is a single pass over the data. If what you actually want is frequency counts rather than filtering, the Find Most Popular tool is the better fit.