How do I toggle the case of a rectangular column region across multiple lines?

Explanation

Visual block mode (<C-v>) selects a rectangular column region, and pressing ~ at the end toggles the case of every character in that exact column range across all selected lines. This is useful for bulk transformations of aligned data — such as switching column headers, toggling the case of a prefix or suffix, or manipulating fixed-width records.

How it works

• <C-v> enters Visual Block mode
• {motion} extends the selection (e.g., jj3l for three lines down and four columns wide)
• ~ toggles case for every character in the selected rectangle

Unlike gU (uppercase all) or gu (lowercase all), ~ flips: lowercase becomes uppercase and uppercase becomes lowercase, character by character.

Example

Given the text:

name:  alice
name:  bob
name:  carol

With the cursor on a in alice, enter <C-v>2j4l~:

name:  ALICE
name:  BOB
name:  CAROL

Tips

• Combine with $ to extend to end of line: <C-v>2j$~ toggles case from the cursor to EOL on each line
• Use gU in visual mode to force uppercase; gu to force lowercase — when you need a deterministic outcome rather than a toggle
• This works in all three visual modes (v, V, <C-v>), but the column precision of block mode makes it uniquely powerful for aligned data