Firebug Lite for Opera 15+
Edit the Page
Toggles the 'Design Mode' so that you can edit the contents of the page.
BuiltWith Technology Profiler
Find out what the website you are visiting is built with using this extension.
Live HTTP Headers
Monitor all HTTP/HTTPs traffic from your browser.
Custom Style Script
Google Analytics Debugger
A browser extension for debugging Google Analytics tracking code
ChroPath for Opera
AutonomIQ offers a developers platform ChroPath to generate and validate unique selectors like relative xpath with iframe support
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!
A browser extension that brings a new GitHub experience
Modify Header Value
Add, modify or remove a header for any request on desired domains.
An extention to show/inspect and analyze fonts in web-pages.
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, ...
Block Yourself from Analytics
Block your Google Analytics™ activity for the websites you own, no more false stats.
WordPress Theme and Plugins Detector
This tool detects theme and plugins used on WordPress sites and displays information about them.
View all HTTP Requests and Responses sent between the Web browser and the Web server.
This extension allows you to add your own custom website specific CSS style sheets.
This extension changes the UserAgent sent by your browser on a per-domain base. You can set up a different UserAgent for a specific domain, but still use the default one otherwise.
ColorHexa - Color Information and Conversion
Color tool converting and providing information about any color.
Quickly view the HTTP headers of the current tab.
Edit with Adobe Photoshop
Adds a context menu item to send image links directly to Adobe Photoshop photo editor
Mini-Browser for Multitasking
Use web utilities/tools without leaving the tab
Website Analysis & SEO Tool
Website SEO audit tool that provides website analysis in SEO, performance, validity, security, accessibility and other criteria.
Random password generator
A simple random password generator for Opera browser
OCR - Image Reader
A powerful optical character recognition (OCR) extension to capture and convert images to text
Shows the response times and uptime of a desired server. Useful to see how performs internet or a wireless access point.
A small extension to validate the markup of current tab
Right Click Validator
Right click on any webpage to validate it using the W3 NUValidator service.
OctoLinker – Links together, what belongs together.