imgproxy preset is a named set of processing options. Presets can be used in [advanced URL format](generating_the_url_advanced.md#preset) to get shorter and somewhat readable URLs.
Processing options should be defined in the same way as you define them in the [advanced URL format](generating_the_url_advanced.md#preset). For example, here is a preset named `awesome` that sets the resizing type to `fill` and resulting format to `jpg`:
A preset named `default` will be applied to each image. Useful in case you want your default processing options to be different from the imgproxy default ones.
Setting `IMGPROXY_ONLY_PRESETS` as `true` switches imgproxy into "presets-only mode". In this mode imgproxy accepts presets list as processing options just like you'd specify them for the `preset` option: