---
title: Auto
summary: Auto enables optimizations based on content negotiation.
url: https://www.fastly.com/documentation/reference/compute/sdks/go/compute-sdk-go/fsthttp/imageopto/enum.Auto/
---

**Kind:** Enum  
**Module:** [imageopto](https://www.fastly.com/documentation/reference/compute/sdks/go/compute-sdk-go/fsthttp/imageopto/)  
**Package:** compute-sdk-go v1.11.0  
**Source:** https://github.com/fastly/compute-sdk-go/blob/d6bf71b04516ed72d6018cab6fff701a865f86e5/fsthttp/imageopto/imageopto.go#L48

```go
type Auto string
```

Alias for `string`.

Auto enables optimizations based on content negotiation.

This functionality is also possible by setting Format to FormatAuto,
which will additionally support JPEGXL output.

## Methods

### String

**Source:** https://github.com/fastly/compute-sdk-go/blob/d6bf71b04516ed72d6018cab6fff701a865f86e5/fsthttp/imageopto/imageopto.go#L56

```go
func (a Auto) String() string
```

**Returns**

`string`