i3wm : start applications on specific workspaces when i3 starts

According to the Arch Wiki i3 page, to autostart an application on a specific workspace, you use i3-msg:

exec --no-startup-id i3-msg 'workspace 1:Web; exec /usr/bin/firefox'

# This is what I use in ie config
# custom variables for workspaces
set $ws1 "1< txt >"
set $ws2 "2> fm "
set $ws3 "3< Web >"
set $ws4 4
set $ws5 5
set $ws6 6
set $ws7 7
set $ws8 8
set $ws9 9


##==================================================##
#                         *** Workspace specific settings ***                     #
##=================================================##
# Assign Workspaces:
assign [class="Firefox"] $ws3
assign [class="Chromium"] $ws3
assign [class="Google-chrome-beta"] $ws3
assign [class="^Geany"] $ws1

NOTE: to apply config, you can use:

i3-msg reload

It's an autostart on workspace launch only, not an autostart when i3 starts but I thought it could be useful.

For example, to launch my web browser in the named second workspace "web" this is what I did in my config :

bindsym $mod+2 workspace 2:web; layout tabbed; exec [ $(ps h -C vimb | wc -l) = 0 ] && /usr/bin/vimb -s

When I hit key 2, my web browser starts but when it's already opened it didn't relaunch it, it just switch to the web workspace.

Note: the layout part can be annoying sometime, it's not a requirement.

For more details see my conf