@mart_e Le RFC 9110 dit "Note that some recipients treat the order in which language tags are listed as an indication of descending priority, particularly for tags that are assigned equal quality values (no value is the same as q=1). However, this behavior cannot be relied upon. " (Le menu de Firefox prétend, à tort, que l'ordre est un ordre de préférence. Mais le RFC permet en effet votre algorithme.)