a late afternoon into the early evening
Seogyo is the real Hongdae: the root of the music, the design, the street fashion, and still where things turn up first. I'd get here from Yeonhui, Yeonnam or Mangwon and work down through it from late afternoon. Walk the famous strip for what it is, but do your going-in off it — and leave before the night the place is known for. That part I wouldn't send you to any more.
One person's route, in the order I'd walk it. No photos, no rankings.
Open this walk in the appStart here — a label as much as a shop. Pick one Korean record. 3F walk-up, opens 2pm.
The coffee I come back to here. It's a semi-basement, so look for the stairs down.
Hongdae's fashion at its most polished. Tax-refund shop, so carry your passport.
The rest of the route — why each stop, in what order, and how long between them — is in the app, along with what to order at every one.
One drink to finish, however you want it. That's the Hongdae I'd still put you in.
Walk it