If Heullimgol is part of your Seoraksan autumn plan, treat the reservation as a required travel step rather than an optional convenience. The Korea National Park Service's current 2026 notice applies the trail-reservation system to the section from Heullimgol Exploration Support Center to Yongso Samgeori.
For the autumn period, the notice lists reservation operation from October 1 through November 30, 2026. The controlled section is 3.1 km and the stated daily capacity is 5,000 people. The normal reservation-entry window is 09:00–14:00, extended in October's peak autumn season to 08:00–15:00.
Reserve through the official KNPS reservation system before traveling to the trailhead. Do not confuse the reservation window with a guarantee that weather, wildfire prevention or other safety controls will never close or restrict the route.
The notice also explains that when the reservation system is not operating, general designated entry-time controls apply. Because mountain controls can change, check Seoraksan notices and the official reservation system again on the travel morning.
This guide is specifically about Heullimgol. It should not be used as a blanket reservation rule for every Seoraksan trail.