Leudachain
HTTP Headers
Quickly view the HTTP headers of the current tab.
Wayback machine website
Online service that have 452 billion web pages saved over time and who is domain tool in context menu
DNS Checker - SEO and Domain Analysis
SEO and Domain Analysis Tool by DNS Checker. Provides SEO Report, Meta Redirects and 404s, Client IP, Domain IP & Geo Location, etc
Random password generator
A simple random password generator for Opera browser
Novibyte Issues Plugin
Jira Issues Management
Website Analysis & SEO Tool
Website SEO audit tool that provides website analysis in SEO, performance, validity, security, accessibility and other criteria.
fonts infos
An extention to show/inspect and analyze fonts in web-pages.
OctoLinker
OctoLinker – Links together, what belongs together.
JavaScript QR Code
Make QR Codes in JavaScript
Edit with Paint.Net
Adds a context menu item to send image links directly to Paint.Net photo editor
Open in Vivaldi
Open current page, link, or all tabs in the Vivaldi browser.
PixelGrid
The tool to overlap your website layout with a grid.
Rabbit URL Opener
Rabbit URL Opener - Bulk URL's Opener Extension just lets you open multiple URLs at once
SelectorsHub
SelectorsHub helps to generate, write and verify the XPath & cssSelector.
WebMoney Advisor Next
Internet users feedback about the sites
Webfonting it!
The simplest extension for working with web fonts
W3C Markup Validation Service
This validator checks the markup validity of Web documents in HTML, XHTML, SMIL, MathML, etc.
Lorem Fill
A webpage form filler that populates context specific random test data into forms elements.
ChroPath for Opera
AutonomIQ offers a developers platform ChroPath to generate and validate unique selectors like relative xpath with iframe support
Sitemap Explorer: Check and View XML Sitemaps
This extension helps you find, inspect, export, and view XML Sitemap files for any site you navigate in a browser.
Open in GIMP photo editor
Adds context menu items to send image links and image files directly to the GIMP photo editor
retire.js
Scanning website for vulnerable js libraries
TechsFound
Find Running Technologies on Website
.no { CSS }
Opera 12 reminiscent Shift-G CSS zapper (use Alt-G)
Tabby Extension
Easily add BookMarks to Tabby from your preferred browser!
Modify O Tabs
Automatically pin or rename a tab of a site you specify or change its icon.
CF-Predictor
This extension predicts rating changes for Codeforces. It shows approximate deltas during and after the contest.
Polypane helper
Open the current page or links in Polypane, the developer tool for responsive web development and design.
Browser Update Watchdog
Notifies you, whenever your browser has been automatically updated.
Nextsense XML Signing Component
Signing XML document.
Check Wordpress Version
WordPress Vulnerability Scanner - Scan for vulnerabilities, version, themes, plugins and much more!
KML/KMZ Viewer
Can be used to view KML/KMZ Files in the browser.