---
title: Auto
summary: Enables optimizations based on content negotiation.
url: https://www.fastly.com/documentation/reference/compute/sdks/rust/fastly/image_optimizer/enum.Auto/
---

**Kind:** Enum  
**Module:** [image_optimizer](https://www.fastly.com/documentation/reference/compute/sdks/rust/fastly/image_optimizer/)  
**Package:** fastly 0.13.1  
**Source:** https://docs.rs/crate/fastly/0.13.1/source/src/image_optimizer.rs#105

```rust
pub enum Auto {
    AVIF,
    WebP,
}
```

Enables optimizations based on content negotiation.

This functionality is also possible by setting [ImageOptimizerOptions::format](https://www.fastly.com/documentation/reference/compute/sdks/rust/fastly/image_optimizer/struct.ImageOptimizerOptions/) to
[Format::Auto](https://www.fastly.com/documentation/reference/compute/sdks/rust/fastly/image_optimizer/enum.Format/), which will additionally support JPEGXL output.

## Variants

### AVIF

If the browser's Accept header indicates compatibility, deliver an AVIF image.

### WebP

If the browser's Accept header indicates compatibility, deliver a WebP image.

## Trait implementations

### impl Clone for Auto

#### clone

**Source:** https://docs.rs/crate/fastly/0.13.1/source/src/image_optimizer.rs#103

```rust
fn clone(&self) -> Self
```

**Parameters**

- `self`: `&Self`

**Returns**

`Self`

### impl Debug for Auto

#### fmt

**Source:** https://docs.rs/crate/fastly/0.13.1/source/src/image_optimizer.rs#103

```rust
fn fmt(&self, f: &mut Formatter<'_>) -> Result
```

**Parameters**

- `self`: `&Self`
- `f`: `&mut $crate::fmt::Formatter`

**Returns**

`$crate::fmt::Result`

### impl Serialize for Auto

#### serialize

**Source:** https://docs.rs/crate/fastly/0.13.1/source/src/image_optimizer.rs#103

```rust
fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>
where
    __S: Serializer,
```

**Parameters**

- `self`: `&Self`
- `__serializer`: `__S`

**Returns**

`_serde::__private228::Result<__S::Ok, __S::Error>`

## Auto trait implementations

- `Freeze`
- `RefUnwindSafe`
- `Send`
- `Sync`
- `Unpin`
- `UnsafeUnpin`
- `UnwindSafe`

## Blanket implementations

- `Any`
- `Borrow<T>`
- `BorrowMut<T>`
- `CloneToUninit`
- `Downcast`
- `DowncastSync`
- `ErasedDestructor`
- `From<T>`
- `Into<U>`
- `IntoEither`
- `Same`
- `ToOwned`
- `TryFrom<U>`
- `TryInto<U>`