Indonesia is generally safe for tourists, but its size and diversity mean risks vary dramatically by region. Bali and tourist areas of Java are well-traveled and relatively safe. Papua and certain parts of Sulawesi and Kalimantan are more challenging and require careful research.
Natural hazards are significant: Indonesia sits on the Ring of Fire with active volcanoes (Merapi, Agung, Krakatoa) and is prone to earthquakes and tsunamis. Register with your embassy and follow local evacuation advice. Water safety: only drink bottled or filtered water. Bali belly (traveler's diarrhea) is common — be careful with street food hygiene.