here's a list of max filesizes for each board:
https://a.4cdn.org/boards.jsonafaik, there is no similar list of accepted file types. since 4chan is an imageboard, most boards only accept image files, i.e. jpg, gif, webm, bmp, png. /tg/ accepts pdfs. apng and a couple other image types are not supported by every some browsers so 4chan does not accept them.
/gif/ and /wsg/ accept webms with sound and larger filesizes because they're the dedicated boards for animated files. /wsr/ and /r/ also accept them so people didn't need to make threads on /gif/ and /wsg/ solely for requests.
there is very little logic in any of this.
