Documentation

auto Automatic

The auto parameter allows imgix to make certain types of adjustments and optimizations automatically. This includes overall image enhancement, changing file formats, compression, and red eye removal.

Auto values can be combined with comma separation, e.g. auto=compress,enhance,format,redeye.

compress

When auto is set to compress, imgix will apply best-effort techniques to reduce the size of the image. This includes altering our normal processing algorithm to apply more aggressive image compression. auto=format is respected, so images will be served in a WebP format whenever possible. If the WebP format is not supported, images that contain transparency will be served in a PNG8 format, if supported, and all others will be served as JPEG. The quality standard is set to 45.

Note: We strive to reduce file size while maintaining as much visual information as possible, so the operations applied are subject to change.

enhance

When auto is set to enhance, the image is adjusted using the distribution of highlights, midtones, and shadows across all three channels—red, green, and blue (RGB). Overall, the enhancement gives images a more vibrant appearance.

The adjustment affects individual images differently as needed, and works best with editorial photography, stock photography, and user-generated content for social media applications.

unset
Example 001
fit=crop&auto=enhance
Example 001
unset
Example 002
fit=crop&auto=enhance
Example 002

format

When auto is set to format, imgix chooses the most appropriate file format for delivering your image based on the requesting web browser. We use a process called automatic content negotiation to compile the various signals available to us—including headers, user agents, and image analytics—to select the optimal image format for your user. This format is served back and the image is correctly cached.

Note: auto=format cannot be set as a Source’s default parameter.

Behind the scenes, these are the steps we take during content negotiation:

  1. Check if your browser supports WebP. If it does, we serve back a WebP image.
  2. Check if the request has a fallback format set by the fm parameter. If it does, we serve back the image in the fallback format.
  3. If the browser is not compatible with either format, serve back the image in its original format.

Please note that this currently only converts images to the WebP format. For a list of browsers that support the WebP format, please see the WebP section on caniuse.com.

To learn more about auto=format and auto content negotiation, read our tutorial.

redeye

When auto is set to redeye, red–eye removal is applied to detected faces.