zellij terminal emulator

December 28, 2025

my tmux setup

I use tmux by default for all my terminal sessions since around 2016 (almost 10 years!): on most days I switch from local desktop keyboard to a laptop and back to run/debug stuff on my desktop. I usually have 4 sessions: various builders, development session, chat session and various one-off investigations.

I have a moderate ~/.tmux.conf:

set -ga terminal-overrides ',xterm*:smcup@:rmcup@'

set -sg escape-time 0

set -g mouse on
bind -T root WheelUpPane   if-shell -F -t = "#{alternate_on}" "send-keys -M" "select-pane -t =; copy-mode -e; send-keys -M"
bind -T root WheelDownPane if-shell -F -t = "#{alternate_on}" "send-keys -M" "select-pane -t =; send-keys -M"

set -g @scroll-speed-num-lines-per-scroll 3

# override default
set -g status-right-length 60 # was 40
set -g status-right '#h, %Y-%m-%d %H:%M' # was something like '"#h", #S'

# Start windows and panes at 1, not 0
set -g base-index 1
setw -g pane-base-index 1

# defatul is ~2000
set-option -g history-limit 10000

# Allow title update from within tmux apps
set-option -g set-titles on

# Host-specific overrides
if-shell "[ -e ~/.tmux.conf.local ]" "source-file ~/.tmux.conf.local"

# Extend default variable list of:
#   "DISPLAY SSH_ASKPASS SSH_AUTH_SOCK SSH_AGENT_PID SSH_CONNECTION WINDOWID XAUTHORITY"
set-option -g update-environment "DISPLAY SSH_ASKPASS SSH_AUTH_SOCK SSH_AGENT_PID SSH_CONNECTION WINDOWID XAUTHORITY   WAYLAND_DISPLAY SWAYSOCK I3SOCK"

# Join current window into a previous one. Should act as inverse of Ctrl-b !
bind-key j "join-pane -s !"

While a bit wordy it’s not a big or complicated setup. And it already contains a few hacks like set -sg escape-time 0 to make ESC button act more responsive. Without it switching modes in vim-like editors has a perceptible delay. I had to press ESC twice to get something out of vim instantly.

a tmux hickup

A month ago I casually sshed on my desktop and was not able to access any of my running tmux sessions:

$ tmux a
open terminal failed: not a terminal
$ tmux
open terminal failed: not a terminal

This happened because tmux updated from 3.5a version to 3.6 and changed its protocol implementation between server (still ran 3.5a) and the client (updated to 3.6). The workaround was trivial: run 3.5 client for a while until the machine get scheduled for a reboot.

I debugged it a bit and find out it was an intentional change. I filed tmux issue #4711 to improve the error message on tmux side. From what I understand at least on linux the change that caused the protocol change was entirely in tmux source code base (around compat/imsg.h / compat/imsg.c files imported from OpenBSD). tmux author decided not to improve the error message.

zellij

This event prompted me to wonder what are the other terminal multiplexers out there.

I tried zellij and am using it for the past month. It’s not a drop-in replacement for tmux but it gets very close for my use cases. I collected a few niceties and a few snags below I encountered while using it.

nice: zellij retains many Ctrl-b tmux-style keys as is

Default zellij configuration is usable as is for a tmux user: Ctrl-b c opens a new pane (as expected), Ctrl-b , renames a tab and so on. That makes it very easy to try zellij without any exploration of config file format.

snag: some keybindings interfere with other applications

zellij uses a few escape-style initial sequences, not just tmux-style Ctrl-b, but also Ctrl-p (panes), Ctrl-n (resizes), Ctrl-h (moves), Ctrl-o (session operations) and a bunch of Alt- ones.

Sometimes these escapes interfere with rich applications like mc, vifm, vim or helix editors.

On the bright side many of them are very convenient, like Alt-n / Alt-f to get a short-lived pane.

Status bar always makes it clear that you got into one of zellij modes. But I had to disable quite a few Ctrl- and Alt--based key bindings in favor of deeper nested Ctrl-b ones in tmux style.

nice: Ctrl-g to disable all the zellij bindings

Given the above zellij has a nice Ctrl-g kill-switch to turn all bindings off (except Ctrl-g itself).

nice: scrollback buffer editing

When in the scrollback scrolling mode (Ctrl-b [ intmux) I sometimes want to save part of the log (or all the contents) into a file. In zellij it’s right there at e key: it opens default editor with full contents.

nice: fast scrolling on copy/paste from the scrollback

Very occasionally I want to copy 100-200 lines of a scrollback and paste it into the browser. I usually use the mouse and in tmux it was very slow for me. I did not always succeed on a ChromeOS terminal.

nice: modern features

I noticed that many features like link uderscores and tooltip pop-ups work inzellij without any configuration just like they work in a host terminal. tmux does not advertise some of them.

snag: CPU / RAM usage is high

zellij can use quite a bit of CPU (and RAM) if the program pipes out a lot of text. For example cat -v /dev/zero command will use 135% CPU on my system with quite a bit of RAM usage (I Ctrl-Ced at 15GiB).

It’s not as bad on more typical multiline workloads.

There is an existing report to get it slightly better.

snag: a banner in the status line

zellij keeps its verbatim name in status bar as an advertisement bit. Which takes away 10 bytes from the status bar (the report).

In theory it’s a one-liner change. But patching it out is not very convenient as zellij implements plugins as wasm binaries and ships the status bar as precompiled .wasm file. I did not manage to rebuild it locally yet.

snag: no tmux-style mouse drag support

I liked how tmux allows you to resize panes just by dragging them. zellij did not implement it yet (the report).

Ctrl-n and arrow keys would have to do for now.

snag: no environment variable clobber support

tmux has a nice variable clobbering feature when DISPLAY, SSH_AUTH_SOCK and a few other variables are updated with variable values of the most recent attached client. As a result ssh-agent, X11 sessions and other things Just Work in newly opened panes. zellij does not have the feature yet (the report’

snag: no support for editing keys in tab editor

In tmux when renaming a tab you can use things like Ctrl-w to delete existing word. zellij dumps a [119;5u escape.

parting words

When I started using zellij I got a lot more than I expected:

But it has quite a few snags as well:

So far zellij is a nice alternative to tmux for me.

Have fun!