The lsu.kr API is a member feature that turns the booking, order and delivery addresses your text program sends to customers into short links. Email-verified members get a key, send the address to POST /api/v1/shorten, and receive the short link back as JSON.
Sign up for free, verify your email, then create a key under My page › API.
https://lsu.kr/api/v1/shortenSend your values in the X-API-Key and X-API-Secret headers. Never put the secret in the URL (query string).
Send the body as JSON {"url": "…"} or as a form (url=…). Choosing a subdomain name or code is not supported via the API.
curl -X POST https://lsu.kr/api/v1/shorten \
-H "X-API-Key: ak_…" \
-H "X-API-Secret: sk_…" \
-H "Content-Type: application/json" \
-d '{"url":"https://example.com/very/long/path?utm_source=newsletter"}'
import requests
r = requests.post("https://lsu.kr/api/v1/shorten",
headers={"X-API-Key": "ak_…", "X-API-Secret": "sk_…"},
json={"url": "https://example.com/very/long/path"}, timeout=30)
print(r.status_code, r.json()["short_url"] if r.ok else r.json())
{
"ok": true,
"code": "Ab3d",
"short_url": "https://lsu.kr/Ab3d",
"target_url": "https://example.com/very/long/path?utm_source=newsletter",
"created_at": "2026-09-25T09:00:00+09:00",
"daily_remaining": 999
}
{
"ok": false,
"error": "check_failed",
"check": "age",
"message": "…"
}
| Status | error value | Meaning |
|---|---|---|
400 | url_required | The url field is required. |
400 | bad_json | The JSON body is malformed. |
401 | auth | The API key or secret is invalid. |
403 | key_blocked | This API key has been blocked. |
403 | member_blocked | API access for this account has been blocked. |
405 | method | Only POST requests are accepted. |
422 | check_failed | The URL failed the safety check (reason code in check). |
429 | rate_limited | Too many requests. Please try again shortly. |
429 | daily_limit | The 24-hour creation limit has been reached. |
429 | too_many_failures | Too many URLs failed the safety check. Please try again later. |
500 | error | Temporary error. Please try again shortly. |
Limits per account: 60 per minute, 1,000 per 24 hours.
Booking confirmations from hair salons, clinics and restaurants, order and delivery-tracking notices from side-dish shops and florists, sign-up addresses that clubs or apartment groups post to Band or group chats: anywhere a different long address has to go out often, per customer or per notice. The sending program fetches a link just before each text goes out and slots it into the message, so staff never have to shorten links one at a time.
A short text holds only about 80 bytes (roughly 40 Korean characters), so a single long address can fill it up. Short links leave room for your shop name and a proper message. See text message length limits for the details.
1) Sign up for free and verify your email. 2) Create a key on the API tab of My page. You get a pair: an API Key starting with ak_ and an API Secret starting with sk_, and one account can keep up to 3 keys in use, handy for separating stores or programs. 3) In your sending program, put the two values in the X-API-Key and X-API-Secret request headers and pass the address to shorten as the url value.
The secret is displayed only once on the issue screen and the server keeps it only in a form that cannot be turned back into the original. If you did not note it down, revoke that key and get a new one. Do not stick the secret on a shared staff PC notepad or in a group chat; keep it inside the sending program settings only.
Addresses sent through the API meet the same standard as on screen. lsu.kr checks that the domain is over 1 month (30 days) old and reachable, is not on the KCSC block list or in URLhaus or OpenPhish, and has no illegal-content keywords, and it also looks at every hand-off address and internal address along the way. If an address fails, you get check_failed and a reason code instead of a link, so hold that text back and check the address first.
After sending, the link is screened again each time a customer taps it and every 3 hours, and reports from three different people block it automatically. How customers can add + to preview a destination is explained in checking short links in smishing texts.
Each account can only create so many links per minute and per 24 hours, with a cap on simultaneous requests, and if rejected addresses pile up in a short time, requests are turned away for a while. When you go over, wait for the Retry-After time given in the response, then carry on; set your sending program to do this.
Accounts that churn out large numbers of links quickly are checked by the operator in person. If it looks like ad spam or smishing, API use can be blocked for the key or the whole account. Operating principles are on the About lsu.kr page.
No. It is free for members; just stay within the per-minute and 24-hour creation limits.
No. The API only produces auto-code links like lsu.kr/Ab3d. Subdomain links with your shop name need to be made on screen by hand.
Revoke that key under My page › API straight away and switch your sending program to a new key. Anything sent with the revoked key is refused from that moment.
Yes. Links made through the API show up in your link list on My page too, where you can check taps, edit the destination or pause the link in the same way.