Very usefull and works perfectly. Used to hide annoying video floating div, or change some css

You have a lot of possibilities with this extension. I wrote more than 15 content scripts that improve my browsing experience tremendously. One of it is to play all animations just for 1 iteration with this content script:
*, *::after, *::before {
animation-iteration-count: 1 !important;
}

Strength:
• Open source. If you are not familiar with "open source", it means this software is more secure. Because its code is publicly available for review and contributions on GitHub at https://github.com/dangkyokhoang/man-in-the-middle
• Attractive GNU General Public License version 3. This means the software code of this extension is owned and supported by a friendly not-for-profit community. Instead of a for-profit corporation. https://github.com/dangkyokhoang/man-in-the-middle/blob/master/LICENSE
• Easy to use
• Inject CSS and or JavaScript into any page
• Easy & quick to create new injections. Organize them. Activate or deactivate any. Which is very useful for quick tests. Such as testing simple CSS or JavaScript tweaks without modifying a site's official theme.
• Trigger inject at DOM event "Loading" or "Loaded" or "Completed"
• Add rules/operations on various type of page requests. Such as blocking, header, response.
• Well documented at https://github.com/dangkyokhoang/man-in-the-middle/blob/master/README.md
• Use any inject in local only or sync
• Fast

Challenge:
• No built-in export or import of configuration using the add-on interface. This would be a useful new feature. Meanwhile this script can manually be added at https://github.com/dangkyokhoang/man-in-the-middle/issues/21
Any volunteer for a patch? I would be happy to contribute testing and documentation if needed.
• Rules are display in the order in which they were created. It is not possible to sort them. This would be a useful new feature. Any volunteer for a patch? Related ticket at https://github.com/dangkyokhoang/man-in-the-middle/issues/7#issue-381636189
I would be happy to contribute testing and documentation if needed.

Using:
• Firefox 78
• Tor Browser 10
• Debian 10 Buster

This addon is great!

It allowed me to test javascript on my client's productive websites, withoutn building up test / staging environments, doing deployment, etc etc - all in a 100% save way. Thank you!

I used it to set a CSS override on Reddit to change the font.

It works, the only problem is that the CSS changes seem to not be applied until a couple seconds after the page is loaded, which is visually jarring.

EDIT: Never mind, I realized I just needed to set it from "completed" to "loading". Maybe "loading" should be the default? Or does that break some scripts?

It helps me to debug minified source because devtools have issues with it. It's very helpful addon!

hay lắm !!!