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Tags are unique identifiers you can add to your emails. They help associate emails with your application. They are passed in key/value pairs. After the email is sent, the tag is included in the webhook event. Tags can include ASCII letters, numbers, underscores, or dashes. Some examples of when to use a tag:
  • Associate the email a “customer ID” from your application
  • Add a label from your database like “free” or “enterprise”
  • Note the category of email sent, like “welcome” or “password reset”
Here’s how you can add custom tags to your emails.

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Add tags on the POST /emails endpoint

import { Resend } from 'resend';

const resend = new Resend('re_xxxxxxxxx');

await resend.emails.send({
  from: 'Acme <onboarding@resend.dev>',
  to: ['delivered@resend.dev'],
  subject: 'hello world',
  html: '<p>it works!</p>',
  tags: [
    {
      name: 'category',
      value: 'confirm_email',
    },
  ],
});

​
Add tags on the POST /emails/batch endpoint

import { Resend } from 'resend';

const resend = new Resend('re_xxxxxxxxx');

const { data, error } = await resend.batch.send([
  {
    from: 'Acme <onboarding@resend.dev>',
    to: ['foo@gmail.com'],
    subject: 'hello world',
    html: '<h1>it works!</h1>',
    tags: [
      {
        name: 'category',
        value: 'confirm_email',
      },
    ],
  },
  {
    from: 'Acme <onboarding@resend.dev>',
    to: ['bar@outlook.com'],
    subject: 'world hello',
    html: '<p>it works!</p>',
    tags: [
      {
        name: 'category',
        value: 'confirm_email',
      },
    ],
  },
]);