SIM, eSIM & WiFi

Roam with your home carrier if your plan includes Korea (T-Mobile, Verizon, EE, Vodafone, etc. usually do). For most others, an eSIM bought online before arrival (Airalo / Holafly / Ubigi, ~$10 to $20 for 3 days) is the lowest-friction option. Skip the airport queue.

Prepaid physical SIM at Incheon (ICN) airport from KT / SKT / LG U+ counters in arrivals. Unlimited 5G data is typically around ₩30,000 to ₩50,000 for 5 to 15 days. eSIM is the same price range and saves the swap. Pocket WiFi only makes sense if your phone is locked.

30-day prepaid SIM from KT / SKT / LG U+ (around ₩50,000 to ₩70,000). For 60 days or more, consider a postpaid plan, but most carriers require an Alien Registration Card (ARC) for postpaid. Without ARC, stick to renewing prepaid or use a SIM-with-USIM service like Chingu Mobile.

When Your plan already covers Korea (T-Mobile, EE, Vodafone, JP carriers, etc.). Quick trips, no friction.

When Phone supports eSIM (iPhone XS+, Pixel 3+, Samsung S20+). Want zero airport faff.

When Standard tourist visit, want full Korean number including SMS.

When Phone is locked / cannot accept other SIMs. Group of 2 to 4 sharing one connection.

Arrivals floor (1F), between Gates 5 and 10.
KT, SKT, LG U+ all have counters.
KT Roaming Center is the most foreigner-staffed (English on hand).
Open ~6am to ~10pm, late arrivals can be tight.

Arrivals (1F), near the central plaza.
Same three carriers.
Quieter than T1 since fewer flights land here, often a faster pickup.

Domestic-international transfer.
KT counter on arrivals, smaller selection.
Most visitors will not arrive here unless connecting from Japan/China low-cost.

eSIMs from Airalo, Holafly, Ubigi.
Physical-SIM-by-mail is also offered by Klook / Trazy with airport pickup vouchers.

Korean law requires passport ID for any SIM activation, even tourist prepaid.
Counters cannot bend this.
Bring it to the airport counter, not in checked luggage.

eSIMs from Airalo / Holafly / Ubigi are data-only by default.
They do not give you a Korean phone number, so you cannot receive SMS.
KakaoTalk, Naver, and Coupang verification will fail.
If you need a Korean number, get a physical prepaid SIM at the airport.

All three carriers have decent 5G in Seoul / Busan / major cities.
Outside metro areas (rural day trips), coverage drops to LTE.
Not a problem for most visitors but matters if you are heading to remote DMZ tours or hiking far from Seoul.

Some "unlimited" prepaid plans throttle after a daily cap (e.g. 5GB/day full speed, then 1Mbps).
Fine for maps + messaging, painful for video calls.
Read the plan card at the counter.

Most subway stations, cafes, and tourist areas have free WiFi (KT_GiGA_WiFi, SK_WiFi, etc.) but they often need a Korean phone number to authenticate.
Cafes are easier, just ask staff for the password.