ReqRes - A hosted REST-API ready to respond to your AJAX requests.

JsonAPI - Application and Data, Languages & Frameworks, and Query Languages

Collabinate - Collabinate provides an API for hosted activity streams, allowing your applications to seamlessly include built-in social feeds, microblogging, and collaboration

JSON Placeholder - JSON Placeholder is a modern platform that provides you online REST API, which you can instantly use whenever you need any fake data.

mocki Fake JSON API - mocki Fake JSON API is an advanced platform that offers you to create API for personal use or testing purposes.

Codegrepper - Codegrepper is a unique platform that provides Fake Rest API, which you can use for prototyping, testing, and many other purposes.