Is syntax keyword case sensitive?

Question

I'm trying to modify the plugin https://github.com/jaxbot/semantic-highlight.vim to highlight variables of differing case with different colours.

Some example configuration the plugin generates:

execute hi! def _semantic0 guifg=#9CD8F7
execute hi! def _semantic1 guifg=#F5FA1D
execute syn keyword _semantic0 json
execute syn keyword _semantic1 JSON

For the above, both json and JSON are highlighted with the same colour.

Is syntax keyword case insensitive?

Answer 1

Apparently it is, from the documentation:

And a keyword with matching case always goes before a keyword with ignoring case.

see: :h syn-define