Supposing you have a rang of cells as below screenshot shown, and you can select blank cell or nonblank cells only in a selection with below steps:

Step 1: Select the range that you will select the blank cells from.

Step 2: Click Home > Find & Select > Go To to open the Go To dialog box. You can also open the Go To dialog box with pressing the F5 key.

Step 3: In the Go To dialog box, click the Special button. See below screenshot:

Step 4: In the Go To Special dialog box, Check the Blanks option. See above screenshot:

Note: If you want to select only nonblank cells only, please check the Constants option.

Step 5: Click OK. Then all blank or nonblank cells in the selection are selected immediately. See the following screenshots:

Quickly fill blank cells with values above/below/left/right or fixed value in Excel

1. Fill all blank cells in this range with values above/below/left/right to each blank cell;
2. Fill all blank cells with certain value or text, such as a special mark "?";
3. Fill all blank cells with liner values.
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If you have Kutools for Excel installed, you can easily select all nonblank cells with content by just one click in Excel. You can do as follows:

Select the range in which you will select only nonblank cells, and click the Kutools > Select > Select Nonblank Cells.

Then you will all nonblank cells with contents are selected at once.