> ## Documentation Index
> Fetch the complete documentation index at: https://developer.upsun.com/llms.txt
> Use this file to discover all available pages before exploring further.

# YAML

> An overview of YAML and its use at Upsun.

[YAML](https://en.wikipedia.org/wiki/YAML) is a human-readable format for data serialization across languages.
This means it's a good fit for human-edited configuration files, like those at Upsun.
You can control nearly all aspects of your project's build and deploy pipeline with YAML files.

Learn what YAML is or, if you're already familiar, what custom tags Upsun offers.

<CardGroup cols={3}>
  <Card title="What YAML is" icon="file-code" href="/docs/core-concepts/yaml/what-is-yaml">
    An introduction to what YAML is and how to create and modify YAML files.
  </Card>

  <Card title="YAML structure" icon="list-tree" href="/docs/core-concepts/yaml/yaml-structure">
    A description of the YAML file for Upsun.
  </Card>

  <Card title="YAML tags" icon="tags" href="/docs/core-concepts/yaml/platform-yaml-tags">
    A description of custom YAML tags available for Upsun files.
  </Card>
</CardGroup>