instagram4j is a Java library that provides an object-oriented interface to Instagram's private (undocumented) API. It supports both mobile and web API endpoints, allowing actions such as logging in with username/password or existing session tokens, fetching profiles, posts, stories, direct messages, searching, posting pictures, liking, commenting, following/unfollowing, and more. The library is structured as a multi-module Gradle project with separate 'mobile' and 'web' modules, each mirroring similar functionality but using different API endpoints (REST for mobile, GraphQL for web). It uses OkHttp for HTTP requests and a custom JSON library. The codebase demonstrates good engineering practices with clear separation of concerns, pagination iterators, and robust error handling. However, there is significant code duplication between the two modules, and the library relies on reverse-engineered endpoints that may break with Instagram updates. The last commit date appears to be in the future (2026), suggesting the repository may be stale or the timestamp is erroneous.