How to prevent the cursor from moving back one character on leaving Insert mode in Vim?

Although I would not recommend changing the default cursor mechanics, one way of achieving the behavior in question is to use the following Insert-mode mapping.

:inoremap <silent> <Esc> <Esc>`^

Here the Esc key is overloaded in Insert mode to additionally run the `^ command which moves the cursor to the position where it had been the last time Insert mode was left. Since in this mapping it is executed immediately after leaving Insert mode with Esc, the cursor is left one character to the right as compared to its position with default behavior.

Unlike some other workarounds, this one does not require Vim to be compiled with the +ex_extra feature.

Although there are tricks to deal with this (such as the ESC mappings mentioned in the previous two posts), there's no consistent way to do this. The reason is that there is no way to determine the method that was used to enter insert mode. Specifically, given the string abcDefg with the cursor on the D:

• If you press i, the insert mode location will be between the c and D. A normal ESC will put the cursor on c; <C-O>:stopinsert<CR> (or the backtick method) will put the cursor on D.

• If you press a, the insert mode location will be between the D and e. A normal ESC will put the cursor on D; <C-O>:stopinsert<CR> will put the cursor on e.

If you REALLY want to do this, you could fudge it with something like this:

let insert_command = "inoremap <ESC> <C-O>:stopinsert<CR>"
let append_command = "iunmap <ESC>"
nnoremap i :exe insert_command<CR>i
nnoremap a :exe append_command<CR>a

BUT: remember that this will only deal with i and a as methods of entry: if you use visual block mode, I, or A or whatever, you'll need to come up with new commands to match (and there are a lot of them). Therefore, I'd strongly recommend you don't do this.

Personally, I'd recommend getting used to the default behaviour. You can easily make it logical for i OR logical for a. If you change the default to logical for i at the expense of logical for a, you'll just get confused when you use a standard vi/vim install.

inoremap <silent> <Esc> <C-O>:stopinsert<CR>

in your .vimrc.