Based on the experience with unnecessarily longer document loading times for inlineXBRL / ESEF reports, a working group of “XBRL International” issued the following technical recommendations on October 27th, 2021:

• • The companies should ensure that the ESEF annual financial report or inlineXBRL / HTML documents are generated directly in the generation process and NOT just generated PDF documents are converted to inlineXBRL / HTML.
  • Authorities, or those collecting the data, should allow font, image and style sheet resources to be included as separate files in a reporting package rather than being embedded in the HTML code.
  • Software manufacturers should: a) avoid or at least optimize the conversion from PDF to inlineXBRL / ESEF in order to avoid an excessive number of HTML elements, b) prefer external resources to embedded resources, c) follow further recommendations for content-visibility: auto CSS property.

Source: XBRL International, Inline XBRL Rendering Performance 1.0, working group note 27 October 2021