It is unclear whether the 4chan alternatives listed are legal in the US, as legality depends on the content of each board and is limited by US law. 8kun (onion), 420chan, Endchan, Kohlchan, iChan, and AnonIB are all listed as alternatives to 4chan, their legality must be determined on a case-by-case basis. Some of these sites may contain content that is illegal in the US. For example, 8kun complies with properly made DMCA requests and all requests that are made are posted on /delete/. Additionally, 420chan has a database of more than 25 million posts and it is probably the only option in the list of sites like 4chan which can be used as a Firefox extension. It is important to note that 4chan is particularly widely regarded as a toxic community and should be used with caution.
spam fails_task lang_mismatch pii not_appropriate hate_speech sexual_content quality toxicity humor helpfulness creativity violence