BuiltWith Technology Profiler
Find out what the website you are visiting is built with using this extension.
Firebug Lite for Opera 15+
PDF API HTML5
GitHub code tree on steroids
Click on any HTML element to get the font info in a popup
Live HTTP Headers
Monitor all HTTP/HTTPs traffic from your browser.
This extension allows you to add your own custom website specific CSS style sheets.
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!
Browse JSON like you do it in Finder.
Edit the Page
Toggles the 'Design Mode' so that you can edit the contents of the page.
Use Redux DevTools in the DevTools
View all HTTP Requests and Responses sent between the Web browser and the Web server.
Corser - Authorize CORS requests
Cross-browser extension for authorizing cross-origin resource sharing (CORS) requests. This extension can be installed on browsers supporting the WebExtensions API (https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions) It intercepts all CORS requests and responses headers, and records/adds/changes their values so as to authorized unauthorized CORS requests. Use this extension only for testing purposes
This extension predicts rating changes for Codeforces. It shows approximate deltas during and after the contest.
Edit with Adobe Photoshop
Adds a context menu item to send image links directly to Adobe Photoshop photo editor
Picture in Play
Indicates whether the `picture` element is in use on a page.
WordPress Theme and Plugins Detector
This tool detects theme and plugins used on WordPress sites and displays information about them.
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.
This will take the URL of the current tab and send it to PageSpeed Insights for a web performance analysis.
Quickly view the HTTP headers of the current tab.
ChroPath for Opera
AutonomIQ offers a developers platform ChroPath to generate and validate unique selectors like relative xpath with iframe support
A small extension to validate the markup of current tab
An extention to show/inspect and analyze fonts in web-pages.
Flag & WHOIS SEO Domain Full Info
Return the domain's IP address , information about security, localization of server, ping, etc.
Google Analytics Debugger
A browser extension for debugging Google Analytics tracking code
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
Outlines nofollow links, detects nofollow and noindex meta tags on webpages. Features website filtering and custom CSS outline styles
SEO Analysis with Seoptimer
Just one click to SEO Analysis with Seoptimer