Unlike Google Image Charts API, the output format (
gif) will not depends on the
chof query parameter but instead on whether or not the chart is animated or not, see the animation section.
However we kept it because some software like Flowdock, Slack or Facebook messenger (and so on...) needs an URL that ends with a valid image extension file to display it as an image. So we recommend you to always use the
chof parameter at the end the URL to support them. Valid values are