How do I make Ctrl-A and Ctrl-X increment and decrement hexadecimal numbers?

Explanation

By adding hex to the nrformats option, you tell Vim to recognise hexadecimal literals such as 0xFF or 0xDEAD when <C-a> or <C-x> is pressed. Without this, Vim treats those characters as plain text and the increment/decrement has no effect.

How it works

• nrformats is a comma-separated list of number formats Vim recognises for <C-a> and <C-x>.
• Supported values include hex (numbers prefixed with 0x or 0X), bin (prefixed with 0b), octal (prefixed with 0), and alpha (single letters).
• Once hex is enabled, placing the cursor anywhere on a hex literal and pressing <C-a> increments it, preserving the 0x prefix and hex digit case.

Example

With :set nrformats+=hex:

uint8_t mask = 0x0F;

With the cursor on 0x0F, pressing <C-a> five times produces:

uint8_t mask = 0x14;

Tips

• Add bin as well (:set nrformats+=hex,bin) to also increment binary literals like 0b1010.
• Many Vim distributions include hex by default; run :set nrformats? to see your current value.
• Use <C-x> to decrement. A count before either command changes multiple values at once: 5<C-a> increments by 5.
• To avoid accidentally incrementing numbers like 007 as octal, remove octal: :set nrformats-=octal.