Webhook.site - Instantly generate a free, unique URL and email address to test, inspect, and automate (with a visual workflow editor and scripts) incoming HTTP requests and emails.
Selection Search - With this extension you can easily search for text you have selected.
MockServer - Easy mocking of any system you integrate with via HTTP or HTTPS.
Context Search - Context Search is a Firefox extension that expands the context menu's 'Search for' item...
Beeceptor - Unblock yourself from API dependencies, and build & integrate with APIs fast. Beeceptor helps you build a mock Rest API in a few seconds.
Trufflepiggy - Quick Search - The all-in-one search addon: just select and search. Find on multiple websites at once. Search via overlay, context menu or omnibar. Featuring anonymous profiles. Easy setup: select from 1000+ user generated searches. Cross-browser sync.