Crossposting is the act of posting the same message to multiple information channels (forums, mailing lists, or newsgroups) in such a way that reading software can relate copies of this message on different information channels. Thus reading software is showing this message only once. This is distinct from multiposting, where copies of the message cannot be related. Crossposting is advantageous to the poster because it increases a number of answers. Suppose that a message does not belong to a distinct topic, and crossposting is not allowed. It may be that the poster sends the message to some channel, but some reader expects it on a different channel and will never receive it. Crossposting and off-topic could be considered spamming. The more channels receive a message, the less is the probability that it is on-topic, so excessive crossposting is generally considered bad practice. In the extreme case, if all messages were crossposted to every unmoderated channel, then every unmoderated channel would look exactly the same. A crossposter can minimize this problem by specifying that all responses be directed to a single channel. Enforcement actions against crossposting individuals vary from simple admonishments up to total lifetime bans. In some cases, on email lists and forums, an individual is put under a Stealth Ban where their posts are distributed back to them as if they were being distributed normally, but the rest of the subscribers are not sent the messages. This is easily detected if the Stealthed individual has two different, and totally non-associated identities in the channel, such that the non-stealthed identity will see a different set of messages, lacking the posts of the stealthed individual, in their view of the channel.

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