minecraft-packets/minecraft-packets/data/pc/1.10.2/from-server/world_border/2.json

An easy way to query PrismarineJS/minecraft-packets

{
  "action": 3,
  "x": 0,
  "z": 0,
  "old_radius": 60000000,
  "new_radius": 60000000,
  "speed": 0,
  "portalBoundary": 29999984,
  "warning_time": 5,
  "warning_blocks": 15
}