The docs state:

format can be set to 'jpg', 'gif', 'png', or 'Auto'.

*Why is it 'Auto' not 'auto'?!


I'm using a variable to define the transform settings:

{% set small = {
    mode:       'fit',
    width:      800,
    height:     600,
    quality:    80,
    position:   'center-center',
    format:     'Auto'
} %}

But Craft errors with:

Imagine\Exception\InvalidArgumentException Saving image in "auto" format is not supported, please use one of the following extensions: "gif", "jpeg", "png", "wbmp", "xbm"

Is this a bug or is my code incorrect?

  • Does this work without the 'format' parameter? Are you using ImageMagik or GD?
    – Matt P
    Mar 14, 2016 at 17:58
  • Yes it works without, so I'm assuming it defaults to Auto. Must be GD as I've not installed ImageMagik. Mar 15, 2016 at 13:34

1 Answer 1


This was an error in the docs. You get the automatic format assignment by default, no need to explicitly set format: 'auto'.

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