HeyGPT is an expansive platform designed to enhance the user's experience with ChatGPT. Still in its beta phase, this progressive web app offers a myriad of features aimed at making interactions more versatile, efficient, and personalized. Notably, it supports the advanced GPT-4 architecture, allowing users to tap into high-quality, nuanced dialogues.

The platform takes interactivity to new heights by enabling functionalities like 'Chat with Audio', 'Chat with Youtube', 'Chat with Docs', and 'Chat with PDFs', to name a few. These features open up a broad spectrum of possibilities, ranging from transcribing audio to chatting with embedded websites, making it much more than a text-based chat interface.

In a bid for complete user autonomy, HeyGPT allows the usage of one's own API keys and avoids the need for a monthly subscription fee. One of its standout features is that it requires no login, ensuring users' chats are stored locally, adding an extra layer of privacy.

The platform is accessible across multiple operating systems, including Mac, Windows, iOS, and Android. It enhances the user interface with options like dark mode and text-to-speech, and even offers chat search functionalities, filtering by tags, and options to favorite or share chats. Users can also export or import chats, customize API settings, and choose from a wide variety of 41 roles and 157 prompts to suit their conversational needs.

Other noteworthy features include markdown format support, multi-language capabilities, and Google search integration. For those looking to push the boundaries even further, HeyGPT offers plugins, multimodal interactions, and auto agents, enhancing the platform's robustness.

In sum, HeyGPT is a comprehensive tool designed to revolutionize the way people interact with ChatGPT, turning it into a multifaceted utility for both personal and professional use.