Example
With “Ignore upper/lower case” on
apples bananas Apples cherries bananas
apples bananas cherries
Typical uses
Cleaning email lists, keyword lists, SKUs, and log files, or merging two lists without double entries. Paste both lists together and remove the duplicates in one pass.
Order is kept
The first time a line appears it stays where it is, and later copies are removed. To put the result in order as well, use Sort alphabetically.
Choosing what counts as a duplicate
Two lines are duplicates only if they match exactly, so small differences matter. “Ignore upper/lower case” treats “Toronto” and “toronto” as the same line, which is what you usually want for names, emails, and keywords. “Ignore spaces at the start and end” catches lines that differ only by a stray space, a common leftover from spreadsheets.
A worked example
Say you have newsletter sign-ups from two events. Paste both lists, one email per line, turn on “Ignore upper/lower case”, and copy the result: each address appears once, in the order it first appeared. To also put the list in order, run it through Sort alphabetically.