Feature: #93908 - Add decoding attribute to images

See forge#93908


TYPO3 now supports the decoding HTML attribute in <img> tags.

Supported browsers choose to decode these images asynchronously to not prevent presentation of other content. This has an effect of presenting non-image content faster. However, the image content is missing on screen until the decode finishes. Once the decode is finished, the screen is updated with the image.

The configuration option is available via TypoScript constants and can be easily adjusted via the TypoScript Constant Editor in the Template module. The default value is an empty string.


TYPO3 frontend decodes images in content elements asynchronously by default when using TYPO3 templates from Fluid Styled Content.

Using the TypoScript constant styles.content.image.imageDecoding, the behavior can be modified generally to be either set to sync, async auto or to an empty value which removes the property.

The Fluid ImageViewHelper and MediaViewHelper have the possibility to set this attribute via <f:image src="{fileObject}" decoding="async"> and <f:media file="{fileObject}" decoding="async">.