Custom Style Script
Live HTTP Headers
Monitor all HTTP/HTTPs traffic from your browser.
Use Redux DevTools in the DevTools
Modify Header Value
Add, modify or remove a header for any request on desired domains.
View all HTTP Requests and Responses sent between the Web browser and the Web server.
Disable cookies for current domain.
Picture in Play
Indicates whether the `picture` element is in use on a page.
Google Analytics Debugger
A browser extension for debugging Google Analytics tracking code
Browse JSON like you do it in Finder.
Get Thumbnails or Image to video YouTube
Make thumbnail previews or images from YouTube videos
Firebug Lite for Opera 15+
Live editor for CSS and LESS - Magic CSS
Live preview of CSS/LESS code with an in-page editor. Autocomplete, convert LESS to CSS, beautify, minify, CSS reloader, linter, ...
Right Click Validator
Right click on any webpage to validate it using the W3 NUValidator service.
Quickly view the HTTP headers of the current tab.
WordPress Theme and Plugins Detector
This tool detects theme and plugins used on WordPress sites and displays information about them.
Edit the Page
Toggles the 'Design Mode' so that you can edit the contents of the page.
Remove cookie(s) for the current domain
Remove cookie(s) for the current site with just one click
This extension allows you to add your own custom website specific CSS style sheets.
Website Analysis & SEO Tool
Website SEO audit tool that provides website analysis in SEO, performance, validity, security, accessibility and other criteria.
Browserling - Cross-browser testing
Cross-browser test websites in the most popular browsers such as Internet Explorer, Edge, Chrome, Firefox, Safari and Opera. Try for free!
Edit with Adobe Photoshop
Adds a context menu item to send image links directly to Adobe Photoshop photo editor
Shows the response times and uptime of a desired server. Useful to see how performs internet or a wireless access point.
SEO Analysis with Seoptimer
Just one click to SEO Analysis with Seoptimer
This extension predicts rating changes for Codeforces. It shows approximate deltas during and after the contest.
ChroPath for Opera
AutonomIQ offers a developers platform ChroPath to generate and validate unique selectors like relative xpath with iframe support
Website Color Changer
Extends the Developer Tools, adding a sidebar for colors manipulation
A small extension to validate the markup of current tab
An extention to show/inspect and analyze fonts in web-pages.