Bernhard Kau

This plugin checks the title of a new post/page or any other post type for uniqueness. The plugin provides a filter <code>unique_title_checker_arguments</code>, which enables you to modify the <code>WP_Query</code> arguments used to find duplicate titles. You may use it to search in more than only current post type for a duplicate title.
This plugin is an enhancement of the <a href="https://wordpress.org/plugins/duplicate-title-checker/" rel="ugc">Duplicate Title Checker</a> by <a href="https://profiles.wordpress.org/ketanajani/" rel="nofollow ugc">ketanajani</a> which only supports posts but not pages or custom post types.
You can contribute to the development of this plugin on <a href="https://github.com/2ndkauboy/unique-title-checker" rel="nofollow ugc">GitHub</a>.
Help translate this plugin into your language on <a href="https://translate.wordpress.org/projects/wp-plugins/unique-title-checker/" rel="nofollow ugc">translate.wordpress.org</a>.

Unique Title Checker

Useful plugin to check duplicate page titles!

A simple plugin that checks the title of any post, page or custom post type to ensure it is unique and does not hurt SEO.

smkn

This plugin notify whether or not duplicate title with AJAX. Search duplication title from same post_type and display this result when you enter the title.

Notify Duplicate Title

This plugin notify whether or not duplicate title.

Unique Title Checker vs Notify Duplicate Title