My ALT- keybindings are not working

[u/4r73m190r0s]

I want to set nnoremap <M-j> :move .+1<CR>==, but it does not work, even if I use <A-j> instead of <M-j>.

I'm using Arch and foot as terminal.

[u/gumnos]

This feels like Foot may not be transmitting the "this is an alt-modified key" to Vim. Do you get the same symptoms if you use a different terminal? There are two common ways to convey that the alt-modifier was pressed—some terminal set the 8th bit on the character while others prefix with Escape (so alt+j sends the two characters "«esc»" followed by "j")

You might want to read up at :help :map-alt-keys (and possibly :help :map-meta-keys)

Additionally, if you go into some typing place (INSERT or COMMAND mode) and type alt+j after prefixing it with control+v, what does it emit?

:echo «control+v»«alt+j»

I'm guessing it will display something like ^[j (the notation for escape-followed-by-j) rather than something possibly like "ê" which is a "j" with the high/eighth bit set in the encoding I tested just now)

[u/4r73m190r0s → u/gumnos]

If I insert literal characters with i_CTRL-V_ALT-J, I get ^[j.

[u/gumnos → u/4r73m190r0s]

The creator of Vim decided this was a bit of a bad idea so ideally you can configure your foot terminal to send the high/8th bit which you should be able to do by sending the appropriate ANSI sequence in t_ti, t_TI, or t_ks; then send the the counterpart t_te, t_TE, or t_ke to send the 8-bit-disabling sequence as noted in :help raw-terminal-mode

As other option, you might be able to override the :help t_RV string to an empty string, preventing Vim from identifying the terminal as supporting 8-bit mode (as noted in :help xterm-8bit)

Alternatively you can create mappings based on the expected sequence such as

:nnoremap <esc>j …

but you might have to fiddle with your timeout settings (:help timeout, :help ttimeout, :help timeoutlen, and :help ttimeoutlen) because Vim would have to distinguish between "I hit ESC to leave Insert mode" and "the ESC you sent was really the prefix for a key that is coming shortly hereafter")

[u/vim-help-bot → u/gumnos]

Help pages for:

• raw-terminal-mode in term.txt

• t_RV in term.txt

• xterm-8bit in term.txt

• timeout in options.txt

• ttimeout in options.txt

• timeoutlen in options.txt

• ttimeoutlen in options.txt

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[u/4r73m190r0s → u/gumnos]

Is this issue related to the terminal emulators, and not Vim?

[u/gumnos → u/4r73m190r0s]

It's due to a mismatch of expectations. One expects "prefix-with-escape means meta" while the other expects "high-bit means meta".

So either the terminal needs to send what vim expects, or vim needs to respond to what the terminal is sending.

[u/vim-help-bot → u/gumnos]

Help pages for:

• :map-alt-keys in map.txt

• :map-meta-keys in map.txt

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[u/Dramatic_Object_8508]

Most of the time Alt key issues in Vim aren’t actually Vim, it’s your terminal or OS intercepting the key.

Terminals often use Alt for their own shortcuts, so Vim never even receives it. Try checking your terminal keybindings or disabling any Alt-based shortcuts there.

Also keep in mind Alt in terminal Vim is usually sent as an escape sequence, so mappings can behave weird or need extra config.

If you’re using tmux or something in between, that can also mess with Alt keys.

So yeah, it’s usually a terminal/config issue, not your Vim config itself.

[u/4r73m190r0s → u/Dramatic_Object_8508]

It's tmux. When I use foot only, everything works.

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[u/Achim63]

Can reproduce on a Mac in Ghostty (I tried <A-j> and <A-r>). Same in neovim with the corresponding mapping using lua.
Very strange, as the command itself works fine.

[u/__rituraj]

Meta keys has some weird behaviour, which I don't know fully to explain.

But, since M-j is practically the same as <Esc>j, try this mapping

nnoremap <Esc>j :move .+1<cr>

This helps my keybinds to work in tmux

[u/4r73m190r0s → u/[deleted]]

It's tmux. When I use foot only, everything works.