if imageboard is an anonymous forum where you have to start the thread [necessarily] with an image, the first one was from a chankoro
i do not remember the name anymore, but it was pornographic and it did not last long
but if we need to consider only the format—as it is known today—it was the tor@kanrinin script, year 2000

some non-japs say it was the lnb based on the filthy work of some tripfags from 4chan
lol this is a complete lie or a huge mistake
first of all that in lbnb the threads [if we could call them that] were not necessarily started with images
the images were attached to posts and this system was much earlier than the creation of lnb
also there were already public scripts much earlier than lnb, such as freebbs
by the way, the script used by the first lbn (and many of the following ones) was older than lbn and had already been used by shiba, for example
there have been other bbses—much earlier than lbn—with the exact same fucking function of attaching images
however, they were all in japanese language, anonymous culture was created by japs, it is an undeniable fact
there was no anonymity on usenet; no imageboards on usenet

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