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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. You can add up to 75 tags per email. 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',
      },
    ],
  },
]);