Those granted the status will have the right to ask questions during the hearings as well as access evidence.
The number of applicants leapt from 300 when the inquiry launched on September 14 to 500 yesterday.
Many survivors are among those to have applied to be core participants, some as part of campaign groups such as Justice4Grenfell but others have applied individually.
Some groups automatically qualified for the status, including survivors of the fire and all individuals who were residents of Grenfell Tower at the time of the blaze.
The inquiry will be split into two phases. The first will examine the immediate causes of the fire and how it came to spread with such deadly effect.
In the second stage, the refurbishment of the tower will be put under the microscope — investigating how and why it came to be wrapped in flammable cladding and insulation.