Find Duplicates - Free Excel Practice Online

This free, interactive exercise teaches you Find Duplicates in Excel through 6 hands-on steps. Instead of watching a video, you type the real formula into a live spreadsheet grid and get instant feedback on every answer. It is part of the Other Excel Skills track and works right in your browser - no Excel install, no download, and no signup.

Practising Find Duplicates this way builds the muscle memory that transfers straight to using Excel at work, in interviews, or for certification prep. Work through the steps above, then keep going with the next lesson to build a complete, free Excel practice course.

What you'll practice in this Find Duplicates lesson

1. These Order IDs have a repeat. Count how many times 1001 appears in A2:A6 with =COUNTIF(A2:A6,1001). - COUNTIF walks the range and counts every cell that equals 1001. There are two of them, so the result is 2. This is how you find duplicates without deleting anything.
2. Now flag the row. In C2, count how many times this Order ID appears: =COUNTIF($A$2:$A$6,A2). Lock the range with dollar signs so it stays put when you copy down. - A2 is 1001, and 1001 appears twice, so C2 returns 2. Copy that formula down and every duplicate ID will show 2 or more. Unique IDs show 1.
3. Mark only later copies, not the first. In C2 type =COUNTIF($A$2:A2,A2)>1. The range grows as you copy down, so the first 1001 is FALSE and the second is TRUE. - The expanding range $A$2:A2 is just A2 on this row, so the count is 1 and 1>1 is FALSE. Two rows later the range includes both 1001s and the same formula returns TRUE.
4. Same expanding formula, now on the second 1001 (row 4). Type =COUNTIF($A$2:A4,A4)>1 in C4. - A2:A4 now contains two 1001s, so the count is 2 and 2>1 is TRUE. This is the row Remove Duplicates would delete.
5. Write a label instead of TRUE/FALSE. In C2: =IF(COUNTIF($A$2:$A$6,A2)>1,"Duplicate","Unique"). - A2 is 1001, which appears twice, so the IF returns Duplicate. Unique IDs (1003) would return Unique. Filter this column to review before you delete anything.
6. Want a clean list and the original left alone? Spill the unique Order IDs with =UNIQUE(A2:A6) in E2. - UNIQUE returns each Order ID once and spills down from E2. The source table is untouched. Use this when you need a dropdown list, not a deleted history.

Find Duplicates practice - FAQ