Grégory Viguier

The plugin adds a new tab in your admin bar with simple but useful indications and tools.
<ul>
<li>Displays the number of queries in your page and the amount of time to generate the page.</li>
<li>Displays the php memory usage and php memory limits (constants <code>WP_MEMORY_LIMIT</code> and <code>WP_MAX_MEMORY_LIMIT</code>).</li>
<li>displays the php version and WP version.</li>
<li>Displays <code>WP_DEBUG</code>, <code>SCRIPT_DEBUG</code>, <code>WP_DEBUG_LOG</code>, <code>WP_DEBUG_DISPLAY</code>, and error reporting values.</li>
</ul>
In your site front-end:
<ul>
<li>Lists the template and all template parts used in the current page (template parts added with <code>get_template_part()</code>). Compatible with WooCommerce’s templates.</li>
<li><code>$wp_query</code>: this will open a lightbox displaying the content of <code>$wp_query</code>. Click the lightbox title to reload the value, click outside the lightbox to close it.</li>
</ul>
In your site administration:
<ul>
<li>Admin hooks: lists some oftenly used hooks (like <code>admin_init</code>). The indicator to the right of the line tells you how many times the hook has been triggered by a callback. A “P” means the hook has a parameter: hover it for more details. Click a hook (on its text) to auto-select its code, for example: click admin_init to select <code>add_action( 'admin_init', '' );</code>.</li>
<li><code>$current_screen</code>: displays the value of 4 properties of this object: <code>id</code>, <code>base</code>, <code>parent_base</code>, <code>parent_file</code>.</li>
<li><code>$...now</code>: displays the value of the well-known variables <code>$pagenow</code>, <code>$typenow</code>, and <code>$taxnow</code>.</li>
<li>On a user profile page, <code>$userdata</code>: : this will open a lightbox displaying the user’s data.</li>
</ul>
You can decide who’s gonna use this plugin (go to your profile page for all the settings). This way, the plugin’s items won’t show up to other users (your client for example). 
Also, a new menu item <code>Code Tester</code> will appear. There you are able to do some tests with your code.

Admin Bar Tools

I'm using this wonderfull tool in all my project and ask my studients to use it when they dev for WordPress.

Make a great job

In all my dev sites

This is one of those plugins I use on every WordPress project. The UI/UX is excellent, it's always there in the admin bar, you don't need to load anything. 

It's just a pity it's not updated to the latest WordPress versions. I sure hope this is not abandoned.

Thanks for sharing your work, @greglone.

So useful. Too bad it's not updated

Adds some small development tools to the admin bar.

Oleg Butuzov

Debug Bar Rewrite Rules adds information about Rewrite Rules (changed via filters) to a new panel in the Debug Bar. This plugin is an extension for <a href="https://wordpress.org/extend/plugins/debug-bar/" rel="ugc">Debug Bar</a>, but it is also can work in standalone mode (as admin tools page). Note: this plugin not able to track <code>add_rewrite_rule</code> function calls, for a reason this function is untraceable.
Once installed, you will have access to the following information:
<ul>
<li>Number of existing rewrite rules</li>
<li>List of rewrite rules</li>
<li>List of available filter hooks that can affect rewrite rules.</li>
<li>List of filters that affects rewrite rules.</li>
<li>Ability to search in rules with highlighting matches.</li>
<li>Ability to test url and see what rules can be applied to it.</li>
<li>Ability to flush rules directly from debug bar panel/tools page.</li>
</ul>

Debug Bar Rewrite Rules

This plugin makes it so easy to debug and even discover WP rewrite rules. Thanks a lot!!

Amazing plugin!

Debug Bar Rewrite Rules adds a new panel to Debug Bar that displays information about WordPress Rewrites Rules (if used).

Admin Bar Tools vs Debug Bar Rewrite Rules