Harmful Digital Communications Act 2015, s 22(1); s 4 (definitions of “digital communication”, “posts a digital communication”)
It’s a criminal offence for someone to cause you serious emotional distress by posting a “digital communication” if they intended to cause you harm. The other person can only be convicted if an ordinary reasonable person in your position would have been harmed by what happened (see below).
The term “digital communication” covers the full range of online, electronic and digital communications. It can include sending you text or emails, or posting online comments about you on Facebook, Twitter or other social media sites or in an online forum or blog, or posting intimate photographs or video of you online (as “revenge porn” for example).