Why doesn't the backspace key work in insert mode?

Question

Trying to delete characters in insert mode with the backspace key sometimes doesn't seem to work. I can backspace sometimes, but at other times it does nothing; the cursor doesn't go to the left, and absolutely nothing seems to happen.

I noticed this using gVim in Windows. The backspace seems to work as expected while using Vim from the terminal in most Linux systems however.

1. Why does this happen?
2. How can I make the backspace key delete characters as usual?
3. Is this behaviour intended as a feature? In other words: are there better alternatives to the backspace to delete characters in insert mode?

Answer 1

tl;dr: Add this to your vimrc to make the backspace work like in most other programs:

In vimscript:

set backspace=indent,eol,start

In lua:

vim.opt.backspace = {'indent', 'eol', 'start'}

---

Longer answer

Though the default behaviour may be surprising, the backspace "not working" can be considered a feature; it can prevent you from accidentally removing indentation, and from removing too much text by restricting it to the current line and/or the start of the insert.

:help 'backspace' tells us:

Influences the working of `<BS>`, `<Del>`, `CTRL-W` and `CTRL-U` in Insert
mode.  This is a list of items, separated by commas.  Each item allows
a way to backspace over something:

value     effect
indent    allow backspacing over autoindent
eol       allow backspacing over line breaks (join lines)
start     allow backspacing over the start of insert; CTRL-W and CTRL-U
          stop once at the start of insert.

So what do these values mean exactly?

indent
Vim adds automatic indentation for many filetypes; by default, you're not allowed to backspace over this; the rules of what is considered to be 'autoindentation' are somewhat subtle, for example, if we would type this (where █ is the cursor):

if (true) {
    █

Backspacing won't work.

But if we would then add a command and the }, and go back up, we are allowed to remove the indentation:

if (true) {
    █fun()
}

This is because in the first example, Vim determined it should add 1 level of indentation when you pressed Enter; but in the second example, Vim didn't autoindent anything, it's just Tab characters or a few spaces.

Also see :help 'autoindent'

eol
This should be the most obvious, pressing Backspace also removes EOL markers (\n or \r\n); if disabled, Backspace will do nothing if you try to delete a EOL marker.

start
This means you can only delete text that you've inserted since insert mode started, and you can't delete any text that was previously inserted.

So what's the default setting?

I noticed this using GVIM in windows. The backspace seems to work as expected while using VIM from the terminal in most Linux systems however.

The reason for this is because many Linux distro's ship with pre-made vimrc files which set some common options. For example on my Arch Linux system I have /usr/share/vim/vimfiles/archlinux.vim with:

set nocompatible
set backspace=indent,eol,start
" ... and a few more...

If you install Vim on Windows, the default is to use the default vimrc and gvimrc that Vim ships with.

The Vim default is an empty value for backspace. The Arch Linux, Debian, CentOS, or $other_distro default may be different.

Normal mode

This question is about Backspace in insert mode, but let me also add some brief remarks about Backspace in normal mode.

In normal mode, the Backspace acts as h, it just goes to the left.

By default, the backspace will go to the previous line if at the start of a line (as if eol was in backspace); you can control this behaviour with the 'whichwrap' option through the b flag (enabled by default).

You can also make backspace delete characters by mapping it to the X command:

nnoremap <BS> X

Answer 2

Just in case anyone is experience not explainable <BS> behavior using ConEmu on Windows, you may have to remap the <BS> key to:

inoremap <Char-0x07F> <BS>
nnoremap <Char-0x07F> <BS>

More information

Answer 3

set backspace=2

is used with v5.4 and earlier. worked for me on mac.

looks like on mac i have v3.2:

$ bash --version
GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin18)
Copyright (C) 2007 Free Software Foundation, Inc.

All versions past 3.2 use the GNU General Public License v3 (GPLv3), which Apple isn't in favor of supporting. A discussion on reddit about this is here.

You can upgrade to the newest Bash with:

brew install bash

this allows to take advantage of programmable completion highlighted here.

Answer 4

If set backspace=indent,eol,start is the last line of your vimrc, none of solutions will work.

Add one more rule after this, eg:

set ruler

Answer 5

None of the solutions worked for me. The problem was that I was using MobaXTerm, which replaced backspace with C-h by default, and had this line in ~/.vimrc:

inoremap <C-h> <Left>

as a result, effectively, all my backspaces were replaced with <Left> keypresses. The solution was to go to MobaXTerm settings -> Terminal -> Local shell settings, and disable "Backspace sends ^H".

Answer 6

In zsh, you might additionally need to put

bindkey -v '^?' backward-delete-char

to your .zshrc file. Relying on the following response.