title: How to restrict text length of a extract in WordPress editor?
body: <p>I need to limit the length of the excerpt field while writing a new post in WordPress. When the limit of characters or words is reached, I would like to show an error message and prevent the user from writing more input. </p>
  
  <p>I found some hints but nothing with actual Wordpress versions. Where should I start to investigate, is there a filter to output a custom excerpt field?</p>