# Extensions

Zed lets you add new functionality using user-defined extensions.

- [Installing Extensions](./extensions/installing-extensions.md)
- [Developing Extensions](./extensions/developing-extensions.md)
  - [Developing Language Extensions](./extensions/languages.md)
  - [Developing Themes](./extensions/themes.md)
  - [Developing Icon Themes](./extensions/icon-themes.md)
  - [Developing Slash Commands](./extensions/slash-commands.md)