A comma-separated list of options for Insert mode completion ins-completion. The supported values are:

menu Use a popup menu to show the possible completions. The menu is only shown when there is more than one match and sufficient colors are available. ins-completion-menu

menuone Use the popup menu also when there is only one match. Useful when there is additional information about the match, e.g., what file it comes from.

longest Only insert the longest common text of the matches. If the menu is displayed you can use CTRL-L to add more characters. Whether case is ignored depends on the kind of completion. For buffer text the 'ignorecase' option is used.

preview Show extra information about the currently selected completion in the preview window. Only works in combination with "menu" or "menuone".

popup Show extra information about the currently selected completion in a popup window. Only works in combination with "menu" or "menuone". Overrides "preview". See 'completepopup' for specifying properties. only works when compiled with the +textprop feature

popuphidden Just like "popup" but initially hide the popup. Use a CompleteChanged autocommand to fetch the info and call popup_show() once the popup has been filled. See the example at complete-popuphidden. only works when compiled with the +textprop feature

noinsert Do not insert any text for a match until the user selects a match from the menu. Only works in combination with "menu" or "menuone". No effect if "longest" is present.

noselect Do not select a match in the menu, force the user to select one from the menu. Only works in combination with "menu" or "menuone".

(default: "menu,preview")