The guidelines also state that children (under-18s) will rarely face criminal charges for offensive tweets or Facebook statuses, for example.
Also if a message is swiftly deleted, blocked by service providers or websites or shown not to be intended for a wider audience, a prosecution is unlikely.
While intended for the CPS to make a decision whether to charge someone or not, the guidelines are also designed to offer early advice to police.
The interim guidelines take effect immediately and are now subject to a consultation process.
More top news
Defence Secretary Michael Fallon has said Boris Johnson's comments about Saudi Arabia "playing proxy wars" were taken out of context.
Home Office files on the Battle of Orgreave are due to be released next year among a host of records relating to the 1984 miners' strike.
Tara Christmas's kitten Elsa was put on a drip when she collapsed last Christmas after eating the leaves of the festive plant.