packer/website/content/docs/templates/hcl_templates/functions/collection/lookup.mdx

---
page_title: lookup function reference
description: The `lookup` function retrieves an element value from a map using the map key. Learn how to use the `lookup` function in Packer templates.
---

⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️
> [!IMPORTANT]  
> **Documentation Update:** Product documentation previously located in `/website` has moved to the [`hashicorp/web-unified-docs`](https://github.com/hashicorp/web-unified-docs) repository, where all product documentation is now centralized. Please make contributions directly to `web-unified-docs`, since changes to `/website` in this repository will not appear on developer.hashicorp.com.
⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️

# `lookup` Function

`lookup` retrieves the value of a single element from a map, given its key.
If the given key does not exist, the given default value is returned instead.

```hcl
lookup(map, key, default)
```

## Examples

```shell-session
> lookup({a="ay", b="bee"}, "a", "what?")
ay
> lookup({a="ay", b="bee"}, "c", "what?")
what?
```

## Related Functions

- [`element`](/packer/docs/templates/hcl_templates/functions/collection/element) retrieves a value from a _list_ given its _index_.