---
title: lookup
summary: Look up the data associated with a particular User-Agent string.
url: https://www.fastly.com/documentation/reference/compute/sdks/rust/fastly/device_detection/fn.lookup/
---

**Kind:** Function  
**Module:** [device_detection](https://www.fastly.com/documentation/reference/compute/sdks/rust/fastly/device_detection/)  
**Package:** fastly 0.13.1  
**Source:** https://docs.rs/crate/fastly/0.13.1/source/src/device_detection.rs#8

```rust
fn lookup(user_agent: &str) -> Option<Device>
```

Look up the data associated with a particular User-Agent string.

**Parameters**

- `user_agent`: `&str`

**Returns**

`Option<Device>`