Modify Header Value
Add, modify or remove a header for any request on desired domains.
GitHub code tree on steroids
Click on any HTML element to get the font info in a popup
Responsive Web Design Tester
Responsive Web Design Tester is a quick and easy way to test your responsive website.
Live HTTP Headers
Monitor all HTTP/HTTPs traffic from your browser.
PDF API HTML5
Use Redux DevTools in the DevTools
Edit the Page
Toggles the 'Design Mode' so that you can edit the contents of the page.
Right Click Validator
Right click on any webpage to validate it using the W3 NUValidator service.
WordPress Theme and Plugins Detector
This tool detects theme and plugins used on WordPress sites and displays information about them.
Website Color Changer
Extends the Developer Tools, adding a sidebar for colors manipulation
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.
Edit with Adobe Photoshop
Adds a context menu item to send image links directly to Adobe Photoshop photo editor
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, ...
This will take the URL of the current tab and send it to PageSpeed Insights for a web performance analysis.
Browse JSON like you do it in Finder.
This extension predicts rating changes for Codeforces. It shows approximate deltas during and after the contest.
Quickly view the HTTP headers of the current tab.
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
An extention to show/inspect and analyze fonts in web-pages.
Picture in Play
Indicates whether the `picture` element is in use on a page.
Shows the response times and uptime of a desired server. Useful to see how performs internet or a wireless access point.
Web Developer Checklist
Analyses any web page for violations of best practices
ChroPath for Opera
AutonomIQ offers a developers platform ChroPath to generate and validate unique selectors like relative xpath with iframe support
ColorHexa - Color Information and Conversion
Color tool converting and providing information about any color.
A webpage form filler that populates context specific random test data into forms elements.
Website Analysis & SEO Tool
Website SEO audit tool that provides website analysis in SEO, performance, validity, security, accessibility and other criteria.