How to highlight cell if value duplicate in same column for google spreadsheet?

Question

Try this:

1. Select the whole column
2. Click Format
3. Click Conditional formatting
4. Click Add another rule (or edit the existing/default one)
5. Set Format cells if to: Custom formula is
6. Set value to: =countif(A:A,A1)>1 (or change A to your chosen column)
7. Set the formatting style.
8. Ensure the range applies to your column (e.g., A1:A100).
9. Click Done

Anything written in the A1:A100 cells will be checked, and if there is a duplicate (occurs more than once) then it'll be coloured.

For locales using comma (,) as a decimal separator, the argument separator is most likely a semi-colon (;). That is, try: =countif(A:A;A1)>1, instead.

For multiple columns, use countifs.

While zolley's answer is perfectly right for the question, here's a more general solution for any range, plus explanation:

    =COUNTIF($A$1:$C$50, INDIRECT(ADDRESS(ROW(), COLUMN(), 4))) > 1

Please note that in this example I will be using the range A1:C50. The first parameter ($A$1:$C$50) should be replaced with the range on which you would like to highlight duplicates!

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to highlight duplicates:

1. Select the whole range on which the duplicate marking is wanted.
2. On the menu: Format > Conditional formatting...
3. Under Apply to range, select the range to which the rule should be applied.
4. In Format cells if, select Custom formula is on the dropdown.
5. In the textbox insert the given formula, adjusting the range to match step (3).

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Why does it work?

COUNTIF(range, criterion), will compare every cell in range to the criterion, which is processed similarly to formulas. If no special operators are provided, it will compare every cell in the range with the given cell, and return the number of cells found to be matching the rule (in this case, the comparison). We are using a fixed range (with $ signs) so that we always view the full range.

The second block, INDIRECT(ADDRESS(ROW(), COLUMN(), 4)), will return current cell's content. If this was placed inside the cell, docs will have cried about circular dependency, but in this case, the formula is evaluated as if it was in the cell, without changing it.

ROW() and COLUMN() will return the row number and column number of the given cell respectively. If no parameter is provided, the current cell will be returned (this is 1-based, for example, B3 will return 3 for ROW(), and 2 for COLUMN()).

Then we use: ADDRESS(row, column, [absolute_relative_mode]) to translate the numeric row and column to a cell reference (like B3. Remember, while we are inside the cell's context, we don't know it's address OR content, and we need the content in order to compare with). The third parameter takes care for the formatting, and 4 returns the formatting INDIRECT() likes.

INDIRECT(), will take a cell reference and return its content. In this case, the current cell's content. Then back to the start, COUNTIF() will test every cell in the range against ours, and return the count.

The last step is making our formula return a boolean, by making it a logical expression: COUNTIF(...) > 1. The > 1 is used because we know there's at least one cell identical to ours. That's our cell, which is in the range, and thus will be compared to itself. So to indicate a duplicate, we need to find 2 or more cells matching ours.

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Sources:

• Docs Editors Help: COUNTIF()
• Docs Editors Help: INDIRECT()
• Docs Editors Help: ADDRESS()
• Docs Editors Help: ROW()
• Docs Editors Help: COLUMN()

Answer of @zolley is right. Just adding a Gif and steps for the reference.

1. Goto menu Format > Conditional formatting..
2. Find Format cells if..
3. Add =countif(A:A,A1)>1 in field Custom formula is
   • Note: Change the letter A with your own column.

From the "Text Contains" dropdown menu select "Custom formula is:", and write: "=countif(A:A, A1) > 1" (without the quotes)

I did exactly as zolley proposed, but there should be done small correction: use "Custom formula is" instead of "Text Contains". And then conditional rendering will work.

Highlight duplicates (in column C):

=COUNTIF(C:C, C1) > 1

Explanation: The C1 here doesn't refer to the first row in C. Because this formula is evaluated by a conditional format rule, instead, when the formula is checked to see if it applies, the C1 effectively refers to whichever row is currently being evaluated to see if the highlight should be applied. (So it's more like INDIRECT(C &ROW()), if that means anything to you!). Essentially, when evaluating a conditional format formula, anything which refers to row 1 is evaluated against the row that the formula is being run against. (And yes, if you use C2 then you asking the rule to check the status of the row immediately below the one currently being evaluated.)

So this says, count up occurences of whatever is in C1 (the current cell being evaluated) that are in the whole of column C and if there is more than 1 of them (i.e. the value has duplicates) then: apply the highlight (because the formula, overall, evaluates to TRUE).

Highlight the first duplicate only:

=AND(COUNTIF(C:C, C1) > 1, COUNTIF(C$1:C1, C1) = 1)

Explanation: This only highlights if both of the COUNTIFs are TRUE (they appear inside an AND()).

The first term to be evaluated (the COUNTIF(C:C, C1) > 1) is the exact same as in the first example; it's TRUE only if whatever is in C1 has a duplicate. (Remember that C1 effectively refers to the current row being checked to see if it should be highlighted).

The second term (COUNTIF(C$1:C1, C1) = 1) looks similar but it has three crucial differences:

It doesn't search the whole of column C (like the first one does: C:C) but instead it starts the search from the first row: C$1 (the $ forces it to look literally at row 1, not at whichever row is being evaluated).

And then it stops the search at the current row being evaluated C1.

Finally it says = 1.

So, it will only be TRUE if there are no duplicates above the row currently being evaluated (meaning it must be the first of the duplicates).

Combined with that first term (which will only be TRUE if this row has duplicates) this means only the first occurrence will be highlighted.

Highlight the second and onwards duplicates:

=AND(COUNTIF(C:C, C1) > 1, NOT(COUNTIF(C$1:C1, C1) = 1), COUNTIF(C1:C, C1) >= 1)

Explanation: The first expression is the same as always (TRUE if the currently evaluated row is a duplicate at all).

The second term is exactly the same as the last one except it's negated: It has a NOT() around it. So it ignores the first occurence.

Finally the third term picks up duplicates 2, 3 etc. COUNTIF(C1:C, C1) >= 1 starts the search range at the currently evaluated row (the C1 in the C1:C). Then it only evaluates to TRUE (apply highlight) if there is one or more duplicates below this one (and including this one): >= 1 (it must be >= not just > otherwise the last duplicate is ignored).

I tried all the options and none worked.

Only google app scripts helped me.

source : https://ctrlq.org/code/19649-find-duplicate-rows-in-google-sheets

At the top of your document

1.- go to tools > script editor

2.- set the name of your script

3.- paste this code :

function findDuplicates() {
  // List the columns you want to check by number (A = 1)
  var CHECK_COLUMNS = [1];

  // Get the active sheet and info about it
  var sourceSheet = SpreadsheetApp.getActiveSheet();
  var numRows = sourceSheet.getLastRow();
  var numCols = sourceSheet.getLastColumn();

  // Create the temporary working sheet
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var newSheet = ss.insertSheet("FindDupes");

  // Copy the desired rows to the FindDupes sheet
  for (var i = 0; i < CHECK_COLUMNS.length; i++) {
    var sourceRange = sourceSheet.getRange(1,CHECK_COLUMNS[i],numRows);
    var nextCol = newSheet.getLastColumn() + 1;
    sourceRange.copyTo(newSheet.getRange(1,nextCol,numRows));
  }

  // Find duplicates in the FindDupes sheet and color them in the main sheet
  var dupes = false;
  var data = newSheet.getDataRange().getValues();
  for (i = 1; i < data.length - 1; i++) {
    for (j = i+1; j < data.length; j++) {
      if  (data[i].join() == data[j].join()) {
        dupes = true;
        sourceSheet.getRange(i+1,1,1,numCols).setBackground("red");
        sourceSheet.getRange(j+1,1,1,numCols).setBackground("red");
      }
    }
  }

  // Remove the FindDupes temporary sheet
  ss.deleteSheet(newSheet);

  // Alert the user with the results
  if (dupes) {
    Browser.msgBox("Possible duplicate(s) found and colored red.");
  } else {
    Browser.msgBox("No duplicates found.");
  }
};

4.- save and run

In less than 3 seconds, my duplicate row was colored. Just copy-past the script.

If you don't know about google apps scripts , this links could be help you:

https://zapier.com/learn/google-sheets/google-apps-script-tutorial/

https://developers.google.com/apps-script/overview

I hope this helps.