User-Agent Switcher is a quick and easy way to switch between user-agents.
This extension lets you easy find the most common Opera actions.
Responsive Web Design Tester
Responsive Web Design Tester is a quick and easy way to test your responsive website.
Quickly view the HTTP headers of the current tab.
Live HTTP Headers
Monitor all HTTP/HTTPs traffic from your browser.
Base64 Encode and Decode
Quickly Encode & Decode Base64 strings
Whats My Info
Shows your IP address and other useful info.