Prompto is an open-source web application that simplifies and streamlines interaction with Large Language Models (LLMs). It allows for seamless switching between different LLMs, offers temperature settings to adjust the creativity and risk levels of the LLM responses, provides both a chatbot interface and a notebook interface, enables the creation of templates for commonly used prompts, and runs entirely in the browser, ensuring a smooth and responsive experience. All settings and chat history are stored only in the browser's local storage, safeguarding user privacy.