Disable syntax hightlighting in vim only for specific buffer - vim

Question

I want to disable syntax highlighting but only for a specific buffer. I tried using modeline at the end of the buffer:
#vim:syntax off:
and
#vim:set syntax=off:
But it is not working.

Answer 1

You need a space (minimally) between the comment symbols and vim for mode lines to be parsed. The first one is also missing an equals sign.
# vim:syntax=off:
Or
# vim:set syntax=off:
If you look at :h modeline you will see that there can be any leading text before vim: but there needs to be whitespace after that text.
The two forms fix the patterns
[text]{white}{vi:|vim:|ex:}[white]{options}
[text] any text or empty
{white} at least one blank character (<Space> or <Tab>)
{vi:|vim:|ex:} the string "vi:", "vim:" or "ex:"
[white] optional white space
{options} a list of option settings, separated with white space
or ':', where each part between ':' is the argument
for a ":set" command (can be empty)
Or
[text]{white}{vi:|vim:|Vim:|ex:}[white]se[t] {options}:[text]
[text] any text or empty
{white} at least one blank character (<Space> or <Tab>)
{vi:|vim:|Vim:|ex:} the string "vi:", "vim:", "Vim:" or "ex:"
[white] optional white space
se[t] the string "set " or "se " (note the space); When
"Vim" is used it must be "set".
{options} a list of options, separated with white space, which
is the argument for a ":set" command
: a colon
[text] any text or empty

Answer 2

tl;dr Switch to the manual mode (:sy manual), enable syntax highlighting with :se syn=ON.
What :sy on (:syntax on) does under the hood is sets the 'syn' ('syntax') option for all the active buffers, and makes vim set the 'syn' option for any new files you open. :sy manual disables the latter automatic behavior. So to enable syntax highlighting for a buffer in the manual mode you've got to: :se syn=ON. To make it clear :sy manual doesn't affect the open buffers. They remain highlighted. But when you later do :se syn=ON, syntax highlighting is enabled for all the active buffers.
In other words if you're going to open a big file, you might want to do :sy manual before that. Then the file will open unhighlighted. If you open another file (you didn't open before in this vim instance, i.e. the inactive buffer doesn't exist) it will also open unhighlighted. To enable syntax for this (supposedly not big) buffer you'd do: se syn=ON. When you no longer need to work with the big file, you do: :sy on.