LINE Messaging API: how it works and how to connect (2026)

What is the LINE Messaging API?

The LINE Messaging API is an HTTPS interface that connects your server to LINE through a LINE Official Account. Your server sends JSON to LINE's endpoints to send messages, and LINE sends JSON to your webhook, a web address on your server, whenever a user does something in the chat.

Once connected, your server can:

• Send push and multicast messages to people who added your Official Account.
• Reply to user events with the reply token LINE includes in each webhook event.
• Receive events from group chats and multi-person chats.
• Fetch profile details for personalization.
• Manage rich menus and Flex Messages, LINE's tappable menus and custom message layouts.

How does the LINE Messaging API work?

Every interaction starts with a webhook. LINE sends an HTTP POST with one or more event objects to the URL you register, and your server answers by replying or by pushing a message later. Verify the signature in the x-line-signature header before you process anything, because LINE creates it with HMAC-SHA256 from the raw request body and your Channel Secret.

LINE warns that your endpoint can receive malicious requests from other sources.

Which webhook events will you handle most often?

LINE sends several kinds of events to one webhook, so a single endpoint can handle all of them. The main ones are messages, follows and unfollows, joins and leaves, and postbacks, and your server decides what to do with each type.

• Message. A user sends a message in a one-on-one, group or multi-person chat.
• Follow and unfollow. A user adds, unblocks or blocks your account, in one-on-one chats only.
• Join and leave. Your account enters or exits a group or multi-person chat.
• Postback. A user triggers a postback action you set up.

What is the difference between reply and push messages?

Reply messages answer a specific event, using the reply token LINE includes in the webhook, and they sit outside your monthly quota. Push, multicast, broadcast and narrowcast messages go out whenever you choose, and each one uses it.

curl -X POST https://api.line.me/v2/bot/message/reply \
-H "Authorization: Bearer {CHANNEL_ACCESS_TOKEN}" \
-H "Content-Type: application/json" \
-d '{"replyToken":"{REPLY_TOKEN}",
"messages":[{"type":"text","text":"Thanks! Your order ships tomorrow."}]}'

A reply token works once. LINE says to use it within one minute of the webhook, and it can change that limit without notice, so reply right away.

A push message needs no reply token. It counts toward your monthly quota.

curl -X POST https://api.line.me/v2/bot/message/push \
-H "Authorization: Bearer {CHANNEL_ACCESS_TOKEN}" \
-H "Content-Type: application/json" \
-d '{"to":"{USER_ID}",
"messages":[{"type":"text","text":"Your package is out for delivery."}]}'

For volume, multicast sends to a list of user IDs with a maximum of 500 per request, broadcast reaches all friends, and narrowcast targets user attributes. Every request can carry a maximum of five message objects.

LINE counts messages by recipient, so one request with four message objects to five people counts as five messages.

Pro Tip: If your plan allows paid extra messages, set the maximum for them in LINE Official Account Manager, so a large campaign can't spend past the number you chose.

Why do businesses use the LINE Messaging API?

Businesses use it because their customers are already on LINE. LY Corporation reports 193 million monthly active users as of 31 March 2026, including 100 million in Japan, 54 million in Thailand and 22 million in Taiwan.

An Official Account reaches those people without a new app, and the API lets software handle the repeat work.

What are LINE Official Accounts and access tokens?

A LINE Official Account is your business identity inside LINE, the account customers add as a friend and chat with. To use the API, you enable it in Settings, then Messaging API, in LINE Official Account Manager, which creates a channel with a Channel ID, a Channel Secret and a channel access token.

Your channel gives you three credentials:

• Channel ID, which identifies the channel.
• Channel Secret, the key used to verify webhook signatures. Treat it like a password.
• Channel access token, which authorizes your API calls.

What are the four channel access token types?

LINE documents four channel access token types: long-lived, v2.1, short-lived and stateless, and they differ in how long they last and whether you can revoke them. Long-lived tokens never expire, stateless tokens last 15 minutes, v2.1 tokens last 30 days or less, and short-lived tokens last 30 days.

How does SleekFlow work with LINE?

SleekFlow connects one LINE Official Account to a SleekFlow account, so your team can send and receive LINE messages without writing code. SleekFlow's Help Center, updated 8 Jul 2025, lists what the connection supports, and it says anything not listed isn't supported.

From the Help Center, you can:

• Connect one LINE Official Account to a SleekFlow account.
• Send and receive messages with customers, in the same omnichannel inbox as your other channels, such as WhatsApp and Instagram.
• Use LINE as a broadcast channel for marketing or announcement messages.

Plan around these limits from the Help Center:

• Getting customers in. Customers add your account as a friend by scanning a QR code or opening a link, and you create both in LINE's account manager.
• Sending. Text of 1,800 characters or fewer, and documents, images, videos and voice notes of 16 MB or less each, plus product messages from your SleekFlow catalog. Payment links need SleekFlow Payment.
• Receiving. Text without bold or italic, images, voice notes and emojis. Location messages, stickers and contact messages aren't supported.
• Who you can push to. Friends at any time, non-friends who messaged you one-on-one in the past 7 days, and group or multi-person chats your account has joined.
• Cost. The Help Center lists a free plan with 500 free messages a month, and extra messages are charged at LINE's pricing tier. LINE's Japan example shows 200 free messages, so check your market's plan.

How do you enable the Messaging API and connect LINE to SleekFlow?

Only SleekFlow Admin users can connect LINE, and you need a LINE Business Account. First you enable the Messaging API in LINE, then you copy a webhook URL from SleekFlow into LINE and paste LINE's credentials back into SleekFlow.

On the LINE side:

1. Open your Official Account in LINE Official Account Manager.
2. Go to Settings, then Messaging API, click Enable Messaging API, enter the provider name and email given in the Help Center article, and accept the terms.

On the SleekFlow side, following the Help Center steps:

1. Open Channels, then LINE Business, click Connect and copy the webhook URL.
2. Back in LINE Official Account Manager, paste the URL into the webhook field and save. LINE's Build a bot page also says to enable Use webhook.
3. Open Response settings and set them as the Help Center screenshot shows. LINE says greeting and auto-reply messages answer on their own when they're enabled, so switch them off if customers get two replies.
4. Copy the Channel ID, Channel Secret and Basic ID (the @ handle) from the Messaging API section in LINE, and paste them into SleekFlow.
5. Enter a channel name, which SleekFlow uses internally, and click Connect.

Where should you start with the LINE Messaging API?

Start with who will build and run it, because the answer sets your route. If you're writing your own bot logic, enable the API on your Official Account, register a webhook and verify every signature before you process events.

If you'd rather have your team reply and broadcast without code, connect the account to SleekFlow.