My mailing list has the same address written with different capital letters; which setting removes those duplicates?
Turn off 'Case-sensitive matching'. The two spellings then count as one line: the first occurrence stays exactly as written and the later one is removed. If you also want every address in lower case, convert the list with the case converter before or after removing duplicates.
Why the same address appears twice
A customer types their email on your order form with a capital first letter because the phone capitalized it, then signs up for your newsletter in lower case. You end up with two entries for what is, in practice, one mailbox, since the big email providers generally ignore letter case in addresses. Send a campaign without cleaning, and that customer gets your offer twice.
A worked example
The list: Ahmed@Gmail.com, then sara@outlook.com, then ahmed@gmail.com.
With the default (case-sensitive matching on): 3 input lines, 3 kept, 0 removed.
With the option off: 3 input lines, 2 kept, 1 removed. What stays is Ahmed@Gmail.com as first written, then sara@outlook.com.
Steps
- Open the Duplicate-line remover and paste the addresses, one per line.
- Untick 'Case-sensitive matching (Apple differs from apple)'.
- Also tick 'Ignore spaces at the start and end of a line when matching', since addresses copied from spreadsheets often carry a stray space.
- Open 'Lines that repeated' to see each repeated address and how many times it appeared, then copy the result.
Want every address in lower case?
The matching option only changes how lines are compared, not what is kept. In our example Ahmed@Gmail.com keeps its capitals. If the campaign software you import into treats them differently, or you simply prefer a uniform list, convert it to lower case first with the Text case converter. The first line then becomes ahmed@gmail.com, and removing duplicates with the default settings gives the same outcome: 2 kept and 1 removed.
What this option does not catch
- A trailing space: we tried ahmed@gmail.com twice, one copy with a space at the end, with case sensitivity off, and both stayed. Turn on ignoring spaces at both ends.
- Dots or a plus sign in the first part of a Gmail address: the tool knows nothing about any email provider's rules, so ahmed.ali and ahmedali are different addresses to it.
- A misspelled address: the tool only removes exact matches; it does not correct or validate addresses.
Remember that a removed address is not lost: it is a second copy of one that stays. Still, keep the original list until the campaign is done, in case you need to check something.
Common questions
Does the option affect Arabic names?
Arabic letters have no upper and lower case, so the option changes nothing for them.
Which copy stays when a line repeats?
Always the first one, as written and in its place.
Is my email list sent to a server?
No, the removal runs inside your browser.