Before you start

An unlocked handset supporting Korean LTE and 5G bands
Passport, for an eSIM or a prepaid SIM
Alien Registration Card, for any postpaid or MVNO line in your own name
A Korean bank account, for auto-debit on most monthly plans

Step-by-step

1
Land connected on a data eSIM
Buy a Korea eSIM before flying and activate it on landing. It covers maps, messaging and navigation while everything else is pending. It is data-only, gives you no Korean number, and cannot be used for identity verification — that is fine as a bridge and a problem as a plan.
Mobile appWho: You, before departureActive on landing
2
Add a prepaid SIM on your passport if you need a number sooner
Carrier counters at Gimhae Airport and in Seomyeon sell prepaid lines with a real 010 number on a passport alone. This is genuinely useful for landlords, agents and delivery drivers. It still will not clear identity verification for banking or Korean apps, because passport-registered lines are not linked to the immigration database in the way verification requires.
In personWho: You5–10 minutes
3
Once the ARC exists, take out a line in your own name
With the ARC and a Korean account you can sign a postpaid contract at a carrier store, or — usually a much better idea — take an MVNO plan. Number portability lets you keep the 010 number you have been using. Carrier stores complete it in half an hour; MVNO sign-up is often online and takes a day or two to activate.
In personWho: YouSame day, or 1–2 days for an MVNO
4
Use it to clear identity verification
Install the PASS verification app, which is the smoothest route for foreign residents, and use it to authenticate into banking, government services and delivery apps. Check that the name on the carrier account matches the ARC exactly — mismatched spacing, hyphens or middle names are the single most common cause of failure.
Mobile appWho: YouMinutes once the line is in your name
5
Order home internet, and ask what the building actually has
Korean fibre is fast and inexpensive by any international standard, and installation is usually quick. What varies is the building: Busan has a lot of older low-rise stock in the hillside districts, some of it wired to a shared connection rather than fibre to the unit. Ask the landlord or agent specifically before signing if your income depends on the line.
OnlineWho: YouDays to two weeks
6
Set up KakaoTalk properly
KakaoTalk is the default channel for almost everything social and administrative in Korea, including messages from your landlord and your building manager. Basic messaging works on a foreign number, but payments, account recovery and the identity-linked features expect a Korean 010 line in your own name.
Mobile appWho: YouSame day

Documents you’ll need

Passport, for eSIM and prepaid
Alien Registration Card, for postpaid and MVNO lines
Korean bank account details for auto-debit
An unlocked, band-compatible handset

Things most newcomers don’t know

The MVNOs resell the same three networks at a fraction of the price, and the coverage is identical.

Korea's budget operators buy wholesale capacity from SKT, KT and LG U+ and pass the saving on, so you are on exactly the same towers with the same speeds. The trade-offs are Korean-language sign-up and a day or two to activate rather than instant in-store setup. Anyone paying a flagship carrier price without needing bundled services is paying several times over for nothing.

Source: community-reported

A prepaid SIM bought on your passport gives you a number but not an identity.

Korean real-name verification checks your line against your registration record, and a passport-registered prepaid line has no such link. So you can call, text and use maps while remaining locked out of banking apps, government portals and most delivery services. Newcomers who assume the number is the point spend weeks confused about why nothing accepts them.

Source: community-reported

Get the name spelling identical across passport, ARC and carrier or verification simply fails.

The check compares strings, not people. A middle name recorded on the ARC but omitted at the phone shop, or a hyphen placed differently, produces a verification failure with an error message that explains nothing. Because the phone contract is usually the last of the three to be created, it is the one to get right — read the screen at the counter before signing.

Source: community-reported

In Busan's hillside districts, the building rather than the plan decides your internet speed.

The sanbok neighbourhoods above the old downtown are full of low-rise buildings from the 1970s and 1980s, and some are served by a shared connection from a basement rather than fibre to each unit. The advertised plan speed then means nothing. If you work from home, ask the agent what the building has and treat the answer as a condition of signing.

Source: community-reported

Common mistakes to avoid

Assuming a prepaid or eSIM number will pass identity verification for banking and Korean apps.
Registering the line in an employer's or a friend's name, leaving you with no control over it.
A name mismatch between passport, ARC and carrier record breaking PASS verification.
Letting a prepaid number lapse and losing the line every verification is bound to.
Signing a lease in an older hillside building without asking what internet actually reaches the unit.

Some of this may be out of date. Spotted something inaccurate? Help us keep it right for the next newcomer.