craigsimps

This is a super-simple plugin which will turn WordPress’ default <code>/?s=query%20terms</code> into <code>/search/query+terms/</code> if you have pretty permalinks enabled.
This is something which I have been placing into a theme include or in a core functionality plugin until recently, but it makes sense to separate this functionality out into an individual plugin so it can be switched on and off independently.
The plugin has no administrative interface or control panel. Activation turns it on, deactivation turns it off. Once activated, performing a search using the standard WP search widget should give you a much nicer search URL.

Simple Search Rewrite

Redirects search results from /?s=query to /search/query/, and converts %20 to +.

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.

Simple Search Rewrite vs Monkeyman Rewrite Analyzer