Cleaning a list: when are two lines really duplicates?
Before deduplicating names or codes, decide what makes two entries equivalent. Similar-looking lines are not necessarily the same record, particularly when identifiers are case-sensitive.
Define equality before deleting entries
Trimming edges can help a list copied from an email, but may change data in which spaces matter. Ignoring letter case may combine Roof and roof, a decision that does not suit every identifier.
ToolRoof treats each line as an item. It does not infer that two names belong to one person, normalize Unicode forms or change digits within the list. Keep the source so you can review removals.
Alphabetical order is not numeric order
Text comparison depends on language. Even with the language settled, names such as item2 and item10 need not follow numeric order: this tool sorts text, not natural numeric sequences.
If arrival order or priority matters, leave sorting off. Deduplication keeps the first retained version under the chosen rules; it does not know which version is newer or more accurate.
References: MDN — Locale-sensitive text comparison with Intl.Collator
Counts aid review but do not certify the list
Compare the before-and-after line counts and inspect similar entries. A reduction may mean empty lines or duplicates were removed, not that incorrect records were discovered.
This is a text tool, not a contact validator, email verifier or record-merging system. Try a non-sensitive example before applying a rule to a working copy that matters.
Example: five lines, two defensible outcomes
The list contains Roof, roof, Roof surrounded by two spaces, an empty line and Floor. Trimming, removing empties and ignoring case leaves Roof followed by Floor: 2 entries from 5 lines.
Keeping case sensitivity with the other options unchanged leaves Roof, roof and Floor: 3 entries. Neither result is universally correct; the choice depends on whether capitalization belongs to the item’s identity or only its presentation.