Abu Dhabi recorded a rise in social media crimes this year as the authorities got tough on abusive comments and 'slanderous speech'.
Prosecutors said 512 criminal cases were reported to them between January and October.
That already exceeds the 357 recorded over 12 months in 2018.
Lead prosecutor Amer Al Amira said the offences included fake adverts, spreading rumours, and posting abusive and slanderous comments online.
"People must be careful about maintaining the expected conduct under the UAE law on social media, as it can have serious consequences on both the offender and those on the receiving end," he said at a talk for journalists and judicial officials.
Offenders found guilty can be subject to sentences ranging from a month to three years in prison, often followed by deportation.
Fines range from at least Dh100,000 to Dh3 million.
On Tuesday, Twitter's Middle East office launched a campaign urging users to help it take on violent imagery, offensive language and illegal streaming of sports games.
Twitter asked users to help identify fake accounts so that its teams can challenge and shut them down, if necessary.
