Dead Link Checker - Check for broken links on any website
Beeceptor - Unblock yourself from API dependencies, and build & integrate with APIs fast. Beeceptor helps you build a mock Rest API in a few seconds.
BrokenLinkCheck - Free Broken Link Checker / Online Dead Link Checking Tool - find bad hyperlinks
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.
LinkChecker - LinkChecker is a free, GPL licensed website validator.
MockServer - Easy mocking of any system you integrate with via HTTP or HTTPS.