# Codex environments

> For the complete documentation index, see [llms.txt](https://learn.chatgpt.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to the page URL.

In the ChatGPT desktop app, open the ChatGPT dropdown and select **Codex**.
When starting a Codex chat, choose where it runs:

- **Local**: work directly in your current project directory.
- **Worktree**: isolate changes in a Git worktree. [Learn more](https://learn.chatgpt.com/docs/environments/git-worktrees).
- **Cloud**: run remotely in a configured cloud environment.

Both **Local** and **Worktree** chats run on your computer.

For the full glossary and concepts, explore the [concepts section](https://learn.chatgpt.com/docs/prompting).


  

> Illustration: New chat composer with Local, Worktree, and Cloud environment options