How does the "format" tag work?

[cortix]

I'm wondering how the format tag works in the background. For example we have a preset like below;

picture.yml

presets:
  default:
    markup: data_auto
    formats: [webp, original] 
    widths: [200, 400, 800, 1200, 1600] 
    media_widths:
      mobile: [200, 400, 600]
      tablet: [400, 600, 800]
    noscript: true
    sizes:
      mobile: calc(100vw - 16px)
      tablet: 80vw

    fallback_width: 800
    fallback_format: original
    size: 800px
    link_source: false 
    dimension_attributes: true 

    attributes:
      parent: 'data-downloadable="true"'
      picture: 'data-volume="11" data-sizes="auto" class="lazyload"'
      img: 'data-sizes="auto" class="lazyload"'
      a: 'class="image-link"'

  webp:
    formats: [webp, original]
    markup: data_picture
    noscript: true
    .....

And suppose we are using default preset. Inside in the default preset, we have format setting. Here, inside the format tag, we are using webp. Does it mean that we should use the webp preset in picture.yml? I mean, does it refer to this -->

presets:
  default:
    ....
    ....
  webp:
    formats: [webp, original]
    markup: data_picture
    noscript: true
    .....

Or does it use the settings in default even though it's webp?

Thanks in advance.

[rbuchberger]

Presets don't merge with the user-created default; all user created presets inherit from the hardcoded default JPT preset (documented here).

You can create that sort of inheritance using yaml anchors and aliases, but it's not usually necessary unles your site is complex.

[cortix]

Thanks a lot