Starting Sunday, sites would need to obtain "informed consent" from visitors before saving cookies on a machine.
Cookies are bits of users' personal data that gets stored when they browse the web. Cookies are at times used to power advertising.
Meanwhile, the Information Commissioner's Office (ICO) would launch a tool for the public to report non-compliant sites.
It is expected that the vast majority of websites would still not be compliant, by the time.
However, according to the ICO, it would not take immediate action over non-compliant sites, and would instead offer guidance.