GPT4All is an open-source software ecosystem that democratizes the training and deployment of powerful and customized large language models (LLMs). It is designed to operate on everyday hardware, making it accessible to a wide range of users. The GPT4All software is optimized to run inference of LLMs with 3-13 billion parameters on the CPUs of laptops, desktops, and servers. It comprises various components including backend, bindings, API, and a chat client, providing a comprehensive suite for AI development. Furthermore, GPT4All offers quantized versions of Transformer Decoder architectures that require less RAM to run locally. These models are compatible with a variety of LLMs, including GPT, GPT-2, GPT-3, GPT-Neo, GPT-J, and more, offering flexibility and versatility in AI application development.