Joining starts locally. U.S. dioceses and campus ministries build delegations a year or more ahead, with deposits, payment plans and sometimes scholarships, and add the Days in the Dioceses in a Korean diocese from July 29 to August 2. A pilgrim without a group can register as an individual, but the organizers encourage joining a delegation, and the lodging, meals and transport card come only with a registered package. The USCCB warns that standard registration is through the official Seoul 2027 site alone, after fraudulent lookalike sites appeared in 2025. The pages on registering for WYD Seoul and on the day-by-day schedule have the mechanics.
The days themselves have a rhythm. Mornings from Wednesday to Friday are catechesis in language groups, usually in a parish or hall with a bishop teaching, then Mass. Afternoons are the Youth Festival across the city, concerts, exhibitions, the Vocations Fair and the Reconciliation Park where hundreds of priests hear confessions. Evenings hold the main events: the Papal Welcome on Thursday August 5, the Way of the Cross on Friday August 6. On Saturday everyone walks to the Vigil site, prays and adores the Eucharist with the Pope, and sleeps there in sleeping bags; Sunday morning is the Closing Mass, after which the next host city is announced.
What people describe afterward is the scale: hundreds of thousands of young Catholics from every country, flags, songs, long walks in heat, poor sleep and confession lines. Dioceses tell pilgrims to expect 6 to 10 miles of walking a day; Seoul expects about 500,000 participants.