Assertible!

Postman helps you be more efficient while working with APIs. Postman is a scratch-your-own-itch project. The need for it arose while one of the developers was creating an API for his project. After looking around for a number of tools, nothing felt just right. The primary features added initially were a history of sent requests and collections. A number of other features have been added since then. Here is a small list.

Eviware, the maker of soapUI, Web Service Testing Leader

Pingdom web site monitoring and other infrastructure for you and instantly let you know when anything goes wrong. Measure uptime, downtime, and the performance of your website as experienced by visitors.

The web developers helper program to create and test custom HTTP requests.Advanced REST client for Google Chrome.

Debug APIs like a human, not a robot.

Runscope helps you monitor, log and measure API usage to solve API problems fast. Automatically monitor APIs without any coding. Runscope provides complete logging for all of your API traffic. Track down troublesome API calls with powerful search. Debug problems by peering into the details of every request and response. Works with any public or private API, behind the firewall or in the cloud.

Powerful, modern HTTP / REST client for Sublime Text. Requester has an expansive feature set, modern UX, powerful, elegant syntax and first class support for API testing and test automation. It runs on macOS, Windows and Linux. Some features:

APICombo is a user-friendly API and website testing and monitoring tool.

Automated API testing for the entire lifecycle. No coding, web-based, actually works.