Custom Style Script
Use Redux DevTools in the DevTools
Click on any HTML element to get the font info in a popup
GitHub on steroids
Browse JSON like you do it in Finder.
Modify request and response headers
WordPress Theme and Plugins Detector
This tool detects theme and plugins used on WordPress sites and displays information about them.
Firebug Lite for Opera 15+
Modify Header Value
Add, modify or remove a header for any request on desired domains.
Google Analytics Debugger
A browser extension for debugging Google Analytics tracking code
Edit the Page
Toggles the 'Design Mode' so that you can edit the contents of the page.
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, ...
Live HTTP Headers
Monitor all HTTP/HTTPs traffic from your browser.
View all HTTP Requests and Responses sent between the Web browser and the Web server.
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!
This extension allows you to add your own custom website specific CSS style sheets.
ChroPath for Opera
AutonomIQ offers a developers platform ChroPath to generate and validate unique selectors like relative xpath with iframe support
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.
OCR - Image Reader
A powerful optical character recognition (OCR) extension to capture and convert images to text
Edit with Adobe Photoshop
Adds a context menu item to send image links directly to Adobe Photoshop photo editor
Website Analysis & SEO Tool
Website SEO audit tool that provides website analysis in SEO, performance, validity, security, accessibility and other criteria.
Shows the response times and uptime of a desired server. Useful to see how performs internet or a wireless access point.
Website Color Changer
Extends the Developer Tools, adding a sidebar for colors manipulation
Remove cookie(s) for the current domain
Remove cookie(s) for the current site with just one click
Get Thumbnails or Image to video YouTube
Make thumbnail previews or images from YouTube videos
This extension predicts rating changes for Codeforces. It shows approximate deltas during and after the contest.