The rules in the office's own words: at least 100 continuous kilometers on the same route to Santiago recognized by the International Pilgrim's Reception Office system, on foot or horseback, or 200 by bicycle; pilgrims starting outside Spain must cover at least 70 km inside Spain; and the credential must be duly stamped along the route travelled, with two stamps a day in the last 100 km, obtained at churches, albergues, hotels, and town halls. The motive must be religious or spiritual; those who state other motives receive a different certificate, and children too young to grasp the pilgrimage's meaning receive a special certificate.
The online step: before or during your walk, open the registration form on oficinadelperegrino.com and enter your personal data, starting point, route, and motive; the office introduced this in 2020 to shorten the queue. On arrival go to Rúa Carretas 33, entered from Rúa García Sabell near the cathedral, and take a QR ticket; the screen and your phone show how the line is moving, so you can go to Mass or lunch and come back. In July, August, and around July 25 the office warns that same-day collection is not guaranteed.
The Compostela itself is free; the optional certificate of distance carries a small fee not published on the pages read. Bring the paper credential or the official digital credential app, your passport, and patience. On December 25 and January 1 the Compostela is issued at the cathedral. The existing pages on what the Compostela is and on how far you must walk give the background; this page is the procedure.