Copilot Arena is an open-source AI programming assistant that provides code auto-completion by integrating various state-of-the-art large language models (LLMs), such as GPT-4o, Codestral, and Llama-3.1. This plugin aims to evaluate the performance of different language models in programming assistance, helping developers find the models that best fit their coding styles. It is free to use and is provided in the form of a Visual Studio Code extension, making it easy to install and use.