Question: Format used in the images for the HTML output

[EchedelleLR]

I was thinking if it was possible to convert images to a same format, optionally and choosing webp for that task, in order to get a final low size output.

[simonrob]

This is a good suggestion - the original plan was to make HTML narratives importable, but since SMIL fulfils that role, HTML exports could be (optionally) compressed. This would most likely only be possible for images, not audio, so there would not be much of a size reduction if you are exporting HTML narratives with audio. But it could lead to a good improvement in file size for image-only narratives. I will take a look when I next get time.