Liker is a plugin for collecting ratings of WordPress posts and pages. The plugin allows you to quickly and accurately gather information about the usefulness of your articles. The plugin can collect ratings in both like and opinion formats. You can choose one of: like / dislike, yes / maybe / no and a simple +1 button. This flexibility of settings allows you to use the plugin for sites of various subjects and in multiple use cases. Many popular sites use similar solutions. For example, Google uses this to evaluate the effectiveness of its reference materials.