Jenkins provides remote access API to most of its functionalities (though some functionalities are programming language-dependent). Currently, it comes in three flavors -
JSON with JSONP support
Remote access API is offered in a REST-like style. That is, there is no single entry point for all features, and instead, they are available under the ".../api/" URL where the "..." portion is the data that it acts on.
For example, if your Jenkins installation sits at interviewbit.com, visiting /api/ will show just the top-level API features available – primarily a listing of the configured jobs for this Jenkins instance.
Or if we want to access information about a particular build, e.g. https://ci.jenkins.io/job/Infra/job/jenkins.io/job/master/lastSuccessfulBuild/,
then go to https://ci.jenkins.io/job/Infra/job/jenkins.io/job/master/lastSuccessfulBuild/api/
and you’ll see the list of functionalities for that build.