Duplicates are kept by default, because in a giveaway they usually mean something: each extra row is an extra chance somebody earned.
When to keep them
If your rules gave extra entries for following, sharing or tagging, the duplicates are the bonus entries. Removing them would quietly cancel the promotion you ran.
When to remove them
If your rules said one entry per person, remove them — but do it before you draw, not after you see the result.
What removal actually does
Removing duplicates keeps the first spelling of each name and adds the chances together. Three rows of @alex become one entry with three chances, so the odds do not change; only the tidiness does. If you want them genuinely reduced to one chance each, remove the duplicates and then turn weights off.
Case sensitivity
Matching is case-insensitive by default, so @Alex and @alex are treated as the same person. That is almost always right for usernames. Turn it off only if your list uses capitalisation to tell entries apart — case-sensitive handles on some platforms, or product and ticket codes.
Duplicates that do not look like duplicates
Exact matching catches the easy half. The rest are the same person wearing a slightly different string, and no tool can decide these for you — you have to look:
- Trailing spaces. “alex ” and “alex” are different text and identical people. Trim the column before you import.
- The @ prefix. If half your list came from comments and half from a form, you will have @alex and alex. Pick one and make the column consistent.
- Display name against handle. “Alex Morgan” and “@alexm” can be one entrant on two rows from two sources.
- Plus-addressed email. alex+giveaway@example.com and alex@example.com deliver to the same inbox and count as one person to almost everybody except a matcher.
- The same person on two platforms. If you ran the giveaway on Instagram and TikTok, somebody entering on both is doing exactly what you asked, and whether that is one entry or two is a rules question, not a data question.
Spam and bot entries are a different problem
Giveaway accounts that enter everything are not duplicates and removing duplicates will not touch them. If you want them out, write the rule before you draw — an account age, a follower floor, a requirement to be following you — apply it to the whole list, and do it before you see who won. Filtering after the draw, on a rule invented for the occasion, is the one thing here that really is unfair.
Do it before the spin, always
The order matters more than the setting. Deciding the duplicate rule while looking at the entry list is defensible; deciding it while looking at the winner is not, and everyone watching can tell the difference.