highimpacttech

This plugin adds .html (or any extension) to your WordPress page and category urls.
You can change the extension from Plugin Setting page.

Custom category and page extensions

Add any ".extension" to WordPress category and page urls.

Jan Fabry

This is a tool to understand your rewrite rules (“Pretty Permalinks”). It is indispensable if you are adding or modifying rules and want to understand how they work (or why they don’t work).
It is only an analyzer, it does not change any rules for you. It parses the rules down to their components and shows the connection with the resulting query variables. It allows you to try out different URLs to see which rules will match and what the value of the different query variables will be (see screenshots).
This plugin was written as a tool to help answering questions about rewrite rules on <a href="http://wordpress.stackexchange.com/" rel="nofollow ugc">the WordPress Stack Exchange</a>.

Monkeyman Rewrite Analyzer

Throws a warning if WP_DEBUG is on, other than that still a very handy tool to check your rewrite rules.

Very useful

Helped me sort some issues with the rewrite rules when developing a plugin. Works fine with WordPress 5.2 and does what you need it too.

Works Great

This plugin is really useful for specific needs.
But unfortunately not maintained anymore... =/
If someone need and update version of this check this out :

https://wordpress.org/plugin/url-rewrite-analyzer

Features:

- Nice and clean interface
- Remove all PHP warning / notices
- Update code structure
- Compatible with latest WP Version
- Light / Old / Dark UI

Good plugins !

Making sense of the rewrite mess. Display and play with your rewrite rules.

Custom category and page extensions vs Monkeyman Rewrite Analyzer