LINE Provider

Configure LINE OAuth for authentication in your Next.js application using NextAuth.js.

Documentation

https://developers.line.biz/en/docs/line-login/integrate-line-login/

Configuration

https://developers.line.biz/console/

LINE Developer Setup

Follow these steps to configure LINE OAuth:

Step 1: Create a LINE Developer Account

Go to LINE Developers Console
Log in with your LINE account
If this is your first time, you'll need to create a developer account

Step 2: Create a Provider

In the LINE Developers Console, click Create under Providers
Enter a provider name (e.g., your company or project name)
Click Create

Step 3: Create a LINE Login Channel

Select your provider and click Create a new channel
Select LINE Login as the channel type
Fill in the required information:

Field	Value
Channel name	Your application name
Channel description	Brief description of your app
App types	Web app (required)
Email address	Your contact email

Click Create

Step 4: Configure LINE Login Settings

In your channel settings, go to the LINE Login tab
Under Web app, toggle it to Enabled
Add the Callback URL:

Environment	Callback URL
Development	`http://localhost:3000/api/auth/callback/line`
Production	`https://YOUR_DOMAIN/api/auth/callback/line`

Step 5: Get Channel ID and Secret

Go to the Basic settings tab
Copy the Channel ID and Channel secret
Add them to your .env.local file:

# .env.local
LINE_CLIENT_ID=your-channel-id
LINE_CLIENT_SECRET=your-channel-secret

Step 6: Apply for Email Permission (Optional)

Tip: Email Address Permission

To retrieve email address, you need to apply for Email address permission. Open LINE Developer Console, go to your Login Channel. Scroll down to find OpenID Connect → Email address permission. Click Apply and follow the instructions.

In your channel, scroll down to OpenID Connect
Find Email address permission
Click Apply
Fill out the application form explaining why you need email access
Wait for approval (usually takes a few days)

Step 7: Publish Your Channel

Once configured, go to the channel's main page
Change the status from Developing to Published
Your LINE Login is now ready for production use

Options

The LINE Provider comes with a set of default options. You can override any of the options to suit your own use case.

LINE Provider options →

Example

// src/core/lib/auth.ts
import LineProvider from "next-auth/providers/line";

export const authOptions: NextAuthOptions = {
  providers: [
    LineProvider({
      clientId: process.env.LINE_CLIENT_ID!,
      clientSecret: process.env.LINE_CLIENT_SECRET!,
    }),
  ],
};

Advanced Configuration

Request Additional Scopes

By default, LINE Login requests profile and openid scopes. To also request email:

// src/core/lib/auth.ts
import LineProvider from "next-auth/providers/line";

export const authOptions: NextAuthOptions = {
  providers: [
    LineProvider({
      clientId: process.env.LINE_CLIENT_ID!,
      clientSecret: process.env.LINE_CLIENT_SECRET!,
      authorization: {
        params: {
          scope: "profile openid email",
        },
      },
    }),
  ],
};

Bot Link Feature

If you have a LINE Official Account, you can prompt users to add your bot:

// src/core/lib/auth.ts
import LineProvider from "next-auth/providers/line";

export const authOptions: NextAuthOptions = {
  providers: [
    LineProvider({
      clientId: process.env.LINE_CLIENT_ID!,
      clientSecret: process.env.LINE_CLIENT_SECRET!,
      authorization: {
        params: {
          bot_prompt: "aggressive", // or "normal"
        },
      },
    }),
  ],
};

Troubleshooting

Common Errors

Error	Solution
Invalid redirect_uri	Check that your Callback URL exactly matches in LINE Developer Console
Channel not found	Verify LINE_CLIENT_ID is correctly set in .env.local
Web app not enabled	Enable Web app in LINE Login tab of your channel settings
Email not returned	Apply for Email address permission and add "email" to scope
Channel is developing	Publish your channel for production use or add test users