@msgly/line

LINE Messaging API adapter for Msgly. Send and receive LINE messages through the unified hub — text, image, video, audio, location, buttons, and quick replies. Supports LINE's free reply-token sends. Zero classes, runs in Node, Next.js, and Edge runtimes.

Install

npm install @msgly/core @msgly/line

Quick start

import express from 'express';
import { createHub } from '@msgly/core';
import { createLineAdapter } from '@msgly/line';

const hub = createHub();

hub.register(
  createLineAdapter({
    channelAccessToken: process.env.LINE_CHANNEL_ACCESS_TOKEN!,
    channelSecret: process.env.LINE_CHANNEL_SECRET!,
  }),
);

await hub.connect({ throwOnFailure: true });

hub.on('message', async (msg) => {
  if (msg.channel === 'line' && msg.content.type === 'text') {
    // Use the free reply token when available
    await hub.send({
      channel: 'line',
      account: msg.account,
      contact: msg.contact,
      content: { type: 'text', text: `You said: ${msg.content.text}` },
      metadata: { replyToken: msg.metadata?.replyToken },
    });
  }
});

const app = express();
app.use(express.json({ verify: (req, _r, buf) => ((req as any).rawBody = new Uint8Array(buf)) }));

const handlers = hub.createWebhookHandler();
app.get('/webhook/:channel', handlers.get);
app.post('/webhook/:channel', handlers.post);

app.listen(3000);

Config

interface LineConfig {
  /** Long-lived channel access token from the Messaging API tab. */
  channelAccessToken: string;

  /** Channel secret from Basic settings — used for webhook signature verification. */
  channelSecret: string;

  /** Override for tests. Defaults to https://api.line.me */
  apiBase?: string;

  /** Override for tests. Defaults to https://api-data.line.me (media endpoints). */
  dataApiBase?: string;
}

Setup (10 minutes)

1. Sign up at developers.line.biz. Create a Provider, then a Messaging API channel inside it.
2. Channel secret. Open the channel → Basic settings → copy Channel secret → set as LINE_CHANNEL_SECRET.
3. Channel access token. Messaging API tab → under "Channel access token (long-lived)" click Issue → copy → set as LINE_CHANNEL_ACCESS_TOKEN.
4. Webhook URL. On the Messaging API tab:
   • Webhook URL: <PUBLIC_URL>/webhook/line
   • Toggle Use webhook to ON
   • Click Verify — should succeed
5. Disable LINE's built-in replies. Same tab:
   • "Auto-reply messages": OFF (otherwise LINE answers before your bot)
   • "Greeting messages": OFF (optional)
6. Add the bot to a chat. Find the bot's QR code on the Messaging API tab → scan with the LINE app → add as friend → message it.

Capabilities

| Feature | Supported | | ------------- | --------- | | text | ✓ | | image | ✓ | | video | ✓ | | audio | ✓ | | file | — | | location | ✓ | | buttons | ✓ | | quick replies | ✓ (max 13, 20-char labels) | | templates | — | | reactions | — | | typing | — |

Reply tokens (free vs push)

LINE's pricing model:

• Reply API (uses a replyToken from the inbound event) — free, doesn't count against your monthly quota.
• Push API (no reply token) — counts against your push quota.

Reply tokens are single-use and expire about 1 minute after the inbound message. Use them when responding immediately:

hub.on('message', async (msg) => {
  if (msg.channel === 'line' && msg.content.type === 'text') {
    await hub.send({
      channel: 'line',
      account: msg.account,
      contact: msg.contact,
      content: { type: 'text', text: 'thanks!' },
      metadata: { replyToken: msg.metadata?.replyToken },  // ← free reply
    });
  }
});

Send without replyToken and the adapter falls back to push automatically.

Sending examples

Image

await hub.send({
  channel: 'line',
  account, contact,
  content: {
    type: 'image',
    mediaRef: { kind: 'url', value: 'https://example.com/cat.jpg' },
  },
});

LINE requires media URLs to be public HTTPS with no auth.

Quick replies

await hub.send({
  channel: 'line',
  account, contact,
  content: {
    type: 'interactive',
    text: 'Pick one:',
    buttons: [
      { id: 'a', label: 'Option A' },
      { id: 'b', label: 'Option B' },
    ],
  },
});

User tap → you receive a text message whose content.text matches the button id.

Common pitfalls

• Bot replies but user doesn't see it: in the LINE Developers Console, "Auto-reply messages" must be OFF. It overrides your bot's responses.
• Invalid reply token: the token expired (>1 min) or was already used. Fall back to push by omitting metadata.replyToken.
• InvalidSignature: LINE_CHANNEL_SECRET is wrong, or your Express app isn't capturing the raw body. The verify callback in express.json() is essential.
• Webhook verify fails in console: server must be running and reachable at the public URL when you click Verify.

Documentation

Full setup walkthrough and multi-channel usage: https://github.com/AyushJain070401/msgly

License

MIT