By default, Neovim uses some internal registers for managing the values that
have been copied (y) and what should be pasted (p). These registers are
independent from the system clipboard, so a value copied from the browser will
not show up when you hit p in Neovim (or Vim).
If you'd like to create a more seamless and cohesive copy/paste experience for yourself, you can instruct Neovim to read from and write to the system clipboard when copy/paste actions happen.
This is accomplished with a provider that instructs Neovim to use the system
clipboard directly for all copy/paste operations.
" ~/.vimrc
set clipboard+=unnamedplus
Setting the clipboard option to include unnamedplus enables that provider
"which transparently uses shell commands to communicate with the system
clipboard or any other clipboard 'backend'." So, for Mac, pbcopy and
pbpaste.
See :h provider-clipboard for more details.