Interior door cores include honeycomb, solid wood, full chipboard, tubular chipboard, and magnesium oxide (MgO) board. Honeycomb doors are lightweight and budget-friendly with basic sound insulation. Solid wood offers durability and a premium feel. Full chipboard balances cost, strength, and acoustics. Tubular chipboard suits mid-range projects, while MgO boards provide superior fire resistance for safety-critical areas.