LMSys is a web application based on Gradio that allows users to try out various open-source models such as Vicuna, Alpaca, WizardLM, MPT-Chat, LLaMA2, StableLM, and FastChat-T5. Additionally, users can compare the performance of these models, and based on the leaderboard, GPT-4 is currently leading with an elo rating of 1206.