Disable cookies for current domain.
Modify Header Value
Add, modify or remove a header for any request on desired domains.
Responsive Web Design Tester
Responsive Web Design Tester is a quick and easy way to test your responsive website.
BuiltWith Technology Profiler
Find out what the website you are visiting is built with using this extension.
View all HTTP Requests and Responses sent between the Web browser and the Web server.
Firebug Lite for Opera 15+
WordPress Theme and Plugins Detector
This tool detects theme and plugins used on WordPress sites and displays information about them.
Use Redux DevTools in the DevTools
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.
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
Browse JSON like you do it in Finder.
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, ...
OCR - Image Reader
A powerful optical character recognition (OCR) extension to capture and convert images to text
Edit the Page
Toggles the 'Design Mode' so that you can edit the contents of the page.
Selenium Page Object Generator
A nimble and flexible Selenium Page Object Model generator to improve agile testing process velocity.
Picture in Play
Indicates whether the `picture` element is in use on a page.
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!
The simplest extension for working with web fonts
Website Analysis & SEO Tool
Website SEO audit tool that provides website analysis in SEO, performance, validity, security, accessibility and other criteria.
This will take the URL of the current tab and send it to PageSpeed Insights for a web performance analysis.
Flag & WHOIS SEO Domain Full Info
Return the domain's IP address , information about security, localization of server, ping, etc.
SEO Analysis with Seoptimer
Just one click to SEO Analysis with Seoptimer
Web Developer Checklist
Analyses any web page for violations of best practices
Quickly view the HTTP headers of the current tab.
Website Color Changer
Extends the Developer Tools, adding a sidebar for colors manipulation
Right Click Validator
Right click on any webpage to validate it using the W3 NUValidator service.
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.