pcdr.marty

Automatically send HTTP Header “last-modified”. 
You can use post last modification time or creation date… (settings in administration)

Last modified header

Automatically send HTTP Header "last-modified".

ggriesser

Optimize the caching behavior of your Website! Smart WordPress by <a href="https://www.velocious.io/" title="Smart WordPress FAQs" rel="nofollow ugc">Velocious.io</a> only reloads pages if something has been changed.
A huge number of users abandon websites that are slow to load. That’s no surprise! No one likes to browse a slow site!
With Smart WP you are able to make your WordPress page load in a better way: Your content gets stored in your visitors browsers and is only reloaded if something changed.
This way you can reduce the performance of your and provide your users with an improved experience.
Your users will love it!
By using Smart WordPress you are able to:
<ul>
<li>change the configuration of your ETags</li>
<li>modify the configuration of the Last-Modified Header</li>
<li>alter the configuration of the Cache-Control Header</li>
</ul>
Acknowledges: This plugin is based on the excellent work by George Notaras. It is a fork of his deprecated Add Headers Plugin – a plugin I have used myself for a bunch of years.

Smart WordPress

Optimize the caching behavior of your Website the easy way and reload pages only if something has been changed.

Last modified header vs Smart WordPress