How is this different from Repeating List Item Remover?

Repeating List Item Remover keeps the first occurrence of every value (even repeated ones) and only drops later repeats, so its output can still contain values that repeated in the input. Unique List Item Finder keeps only values that appeared exactly once anywhere in the input, excluding any value that repeated at all.

What if a value appears exactly twice?

It's excluded entirely, since "unique" here means occurring exactly once; two occurrences means it repeats and belongs to Unique List Item Remover's output instead.

What happens if every item repeats?

You'll get a clear error saying no items appear exactly once, rather than a silently empty result.

Unique List Item Finder - Find Items That Appear Once

Overview

Introduction

Sometimes what you need is the opposite of finding duplicates: isolating the values that only show up once, for example to spot one-off outliers in a dataset.

Unique List Item Finder filters a list down to exactly those single-occurrence items.

What Is Unique List Item Finder?

A singleton extractor: it counts every distinct value in your list and keeps only the ones whose total count is exactly one.

The result preserves the original list order, since each qualifying value only ever occupies a single position.

How Unique List Item Finder Works

The input is split into items using the selected separator, then each distinct value's occurrence count is tallied.

Items whose value's total count equals exactly one are kept in the output; everything else, including values that repeat two or more times, is dropped.

When To Use Unique List Item Finder

Use it to spot one-off values in a dataset, for example a single unusual log entry among many repeated ones.

It's the natural complement to Unique List Item Remover, which keeps the opposite set.

Often used alongside Unique List Item Remover, Repeating List Item Remover and Repeating List Item Finder.

Features

Advantages

Preserves original list order for the values it keeps.
Clear, explicit definition of "unique" as exactly-once occurrence, not just first-seen.

Limitations

Comparison is exact and case-sensitive with no trimming applied, so near-duplicates with stray whitespace won't be merged.
Doesn't show occurrence counts for the excluded, repeating values; use Repeating List Item Finder for that.

Examples

Filtering out repeats

Input

apple
banana
apple
cherry

Output

banana
cherry

"apple" repeats and is excluded; "banana" and "cherry" each appear once and are kept.

No unique items remain

Input

a
a
b
b

Output

(error: every item repeats)

Every value in this list appears twice, so there are no exactly-once items to report.

Best Practices & Notes

Best Practices

Run Repeating List Item Finder first if you also want to see counts for the values this tool excludes.
Use a custom separator if your source list isn't newline- or comma-delimited.

Developer Notes

Builds a `Map<string, number>` frequency table over the split items, then filters the original array with `items.filter(item => counts.get(item) === 1)`, which naturally preserves original order since it's a direct filter, not a rebuild.

Unique List Item Finder Use Cases

Finding one-off outlier entries in a pasted dataset
Isolating values that need individual review because they don't fit an expected pattern of repetition
Cleaning survey or log data down to just the singleton responses

Common Mistakes

Assuming this returns every distinct value; it explicitly excludes anything that repeats, even if you only wanted duplicates removed (see Repeating List Item Remover for that instead).
Expecting whitespace or case differences to be normalized before comparison; they aren't.

Tips

If the result seems too short, double check whether some "unique-looking" values actually have hidden duplicate whitespace elsewhere in the list.
Pair with List Comparer to check whether your unique values also exist in a second reference list.

Unique List Item Finder