How do I move to the diagonally opposite corner of a blockwise visual selection?

Explanation

In Visual-Block mode (<C-v>), pressing O moves the cursor to the diagonally opposite corner of the rectangular selection. This lets you adjust both the row and column extent of the block at once — unlike o, which only toggles between the two ends on the same column.

How it works

• o — in any visual mode, moves the cursor to the other end of the selection (same column for block; opposite line end for linewise; opposite end for charwise)
• O — only in Visual-Block: moves to the opposite corner diagonally, so cursor jumps from (top-left ↔ bottom-right) or (top-right ↔ bottom-left)

A block selection has four corners. o toggles between two corners on the same row edge. O toggles to the corner on the opposite column edge, giving you independent control over all four corners.

Example

Start a block selection from column 3 to column 8, rows 1–4:

[ cursor at top-left corner ]
foo |bar| baz
foo |bar| baz
foo |bar| baz
foo |bar| baz

• Press o → cursor jumps to bottom-left corner (same column, different row)
• Press O → cursor jumps to top-right corner (different column, same row)

This lets you reshape the block from any of its four corners without restarting the selection.

Tips

• Use O to quickly extend or shrink the column span of a block selection
• Combine with o to navigate all four corners: each o and O press gives you a different anchor point
• Practical use: select a block of code, press O to reposition to the right edge, then extend rightward with l