Add Headers Plugin WordPress, Download, Install
November 14, 2016
Adds the ETag, Last-Modified, Expires and Cache-Control headers to HTTP responses generated by WordPress. [DEPRECATED]
Add Headers Download Now
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Originals Link WordPress.org
https://wordpress.org/plugins/add-headers/
How to Install Add Headers Plugin, Manually
Add-Headers can be easily installed through the plugin management interface of WordPress.
Video
Plugin Not Working?
If any errors or problems with the plug-in then write comments.