The alliance, which used to organise June 4 vigils, said its website, Facebook, Twitter, Instagram and YouTube entries would be taken down at 10pm, although it noted that it doesn’t own or operate the June 4 online museum.
It said in a statement that last Friday, police ordered the removals within a week, citing national security rules.
The alliance added that it will start a new Facebook page to disseminate information.
The alliance is facing a charge of inciting subversion of state power, as are three of its leaders or former leaders – Lee Cheuk-yan, Albert Ho and Chow Hang-tung.