Postman is a tool for working with REST APIs that describes itself as an API Development Environment. It can be used to interactively test API requests in the process of building software. For example, Postman can be used to test requests that pull data from the Internet Archive's Open Library Books API, to manually explore data available from an OAI-PMH server, or to interact with the Digital Public Library of America's API. Postman understands JSON, XML, and HTML data and prints responses for easier consumption by humans. Developers building software that provides a REST API can use Postman's testing features to run a scripted series of requests against their software, verifying that it produces the correct output. Sets of requests can be saved in workspaces, which can then be shared with collaborators and co-workers. These workspaces can be augmented with documentation about each included API call. Postman is available for Windows, macOS, and Linux computers.