fastest way to delete empty rows in excel?

When there isn't a column that's always filled, a helper column does it safely. Put =COUNTA(A2:Z2) next to the data (stretch the range to cover all your columns), fill it down, filter that column to 0 and delete those rows. Only rows that are completely empty get a 0, so half-filled ones are safe. If you do this a lot, Power Query has a Remove Blank Rows button too.

Select the range, press Ctrl+G, click Special, pick Blanks, OK. Every empty cell is now selected. Then Home > Delete > Delete Sheet Rows. Careful though: that selects blank CELLS, not blank rows. If some rows are only half empty, it will delete those too and take your data with them. If that's possible in your sheet, turn on a filter instead, filter one column that is always filled in on real rows to show only (Blanks), select the visible rows and delete them, then clear the filter.