How do I paste a register in insert mode without triggering auto-indent?

Explanation

When you use <C-r>a in insert mode to paste register a, Vim inserts the text as if you typed it character by character. This means auto-indent, abbreviations, and mappings all fire, often mangling pasted code with unwanted indentation. <C-r><C-o>a inserts the register contents literally, bypassing all of that.

How it works

• <C-r> — enters register-insert mode on the command line or in insert mode
• <C-o> — modifier that tells Vim to insert the text literally, without processing it as typed characters
• {reg} — any register name (a-z, ", 0, +, etc.)

The key difference is that <C-r>a simulates keystrokes (triggering 'autoindent', 'smartindent', 'cindent', abbreviations, and insert-mode mappings), while <C-r><C-o>a inserts the raw text directly.

Example

Suppose register a contains a multi-line code block and you have autoindent enabled:

# Using <C-r>a inside an indented block:
    if condition:
        def foo():
            return bar
            # extra unwanted indent on each line!

# Using <C-r><C-o>a inside an indented block:
    if condition:
    def foo():
        return bar
        # indentation preserved exactly as yanked

Tips

• This is especially valuable when pasting into already-indented code with cindent or smartindent active
• Also works on the command line (: prompt) — <C-r><C-o>/ pastes the search register literally
• For a similar effect in normal mode, use ]p to paste with adjusted indentation or "ap with set paste