WhatsApp has been fined €225m (£193m) by Ireland's data watchdog for breaching privacy regulations.
It is the largest fine ever from the Irish Data Protection Commission, and the second-highest under EU GDPR rules.
Facebook, which owns Whatsapp, has its EU headquarters is in Ireland, and the Irish regulator is the lead authority for the tech giant in Europe.
Whatsapp said it disagrees with the decision, and the severity of the fine, and plans to appeal.
The fine relates to an investigation which began in 2018, about whether WhatsApp had been transparent enough about how it handles information.
The issues involved were highly technical, including whether WhatsApp supplied enough information to users about how their data was processed and if its privacy policies were clear enough.
Those policies have since been updated several times.
"WhatsApp is committed to providing a secure and private service," a company spokesperson said.
"We have worked to ensure the information we provide is transparent and comprehensive and will continue to do so. We disagree with the decision today regarding the transparency we provided to people in 2018 and the penalties are entirely disproportionate."
GDPR rules allows for mammoth fines of up to 4% of the offending company's global turnover.