> ## Documentation Index
> Fetch the complete documentation index at: https://resend.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Managing Tags

> Add unique identifiers to emails sent.

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.

## Add tags on the `POST /emails` endpoint

<CodeGroup>
  ```ts Node.js {10-15} theme={"theme":{"light":"github-light","dark":"vesper"}}
  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',
      },
    ],
  });
  ```

  ```php PHP {8-13} theme={"theme":{"light":"github-light","dark":"vesper"}}
  $resend = Resend::client('re_xxxxxxxxx');

  $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',
      ],
    ]
  ]);
  ```

  ```python Python {10-12} theme={"theme":{"light":"github-light","dark":"vesper"}}
  import resend

  resend.api_key = "re_xxxxxxxxx"

  params: resend.Emails.SendParams = {
    "from": "Acme <onboarding@resend.dev>",
    "to": ["delivered@resend.dev"],
    "subject": "hello world",
    "html": "<p>it works!</p>",
    "tags": [
      {"name": "category", "value": "confirm_email"},
    ],
  }

  email = resend.Emails.send(params)
  print(email)
  ```

  ```rb Ruby {10-12} theme={"theme":{"light":"github-light","dark":"vesper"}}
  require "resend"

  Resend.api_key = "re_xxxxxxxxx"

  params = {
    "from": "Acme <onboarding@resend.dev>",
    "to": ["delivered@resend.dev"],
    "subject": "hello world",
    "html": "<p>it works!</p>",
    "tags": [
      {"name": "category", "value": "confirm_email"}
    ]
  }

  sent = Resend::Emails.send(params)
  puts sent
  ```

  ```go Go {16} theme={"theme":{"light":"github-light","dark":"vesper"}}
  import (
  	"fmt"

  	"github.com/resend/resend-go/v3"
  )

  func main() {
    ctx := context.TODO()
    client := resend.NewClient("re_xxxxxxxxx")

    params := &resend.SendEmailRequest{
        From:        "Acme <onboarding@resend.dev>",
        To:          []string{"delivered@resend.dev"},
        Text:        "<p>it works!</p>",
        Subject:     "hello world",
        Tags:        []resend.Tag{{Name: "category", Value: "confirm_email"}},
    }

    sent, err := client.Emails.SendWithContext(ctx, params)

    if err != nil {
      panic(err)
    }
    fmt.Println(sent.Id)
  }
  ```

  ```rust Rust {14} theme={"theme":{"light":"github-light","dark":"vesper"}}
  use resend_rs::types::{CreateEmailBaseOptions, Tag};
  use resend_rs::{Resend, Result};

  #[tokio::main]
  async fn main() -> Result<()> {
    let resend = Resend::new("re_xxxxxxxxx");

    let from = "Acme <onboarding@resend.dev>";
    let to = ["delivered@resend.dev"];
    let subject = "hello world";

    let email = CreateEmailBaseOptions::new(from, to, subject)
      .with_html("<p>it works!</p>")
      .with_tag(Tag::new("category", "confirm_email"));

    let _email = resend.emails.send(email).await?;

    Ok(())
  }
  ```

  ```java Java {17} theme={"theme":{"light":"github-light","dark":"vesper"}}
  import com.resend.*;

  public class Main {
      public static void main(String[] args) {
          Resend resend = new Resend("re_xxxxxxxxx");

          Tag tag = Tag.builder()
                  .name("category")
                  .value("confirm_email")
                  .build();

          SendEmailRequest sendEmailRequest = SendEmailRequest.builder()
                  .from("Acme <onboarding@resend.dev>")
                  .to("delivered@resend.dev")
                  .subject("hello world")
                  .html("<p>it works!</p>")
                  .tags(tag)
                  .build();

          SendEmailResponse data = resend.emails().send(sendEmailRequest);
      }
  }
  ```

  ```csharp .NET {12} theme={"theme":{"light":"github-light","dark":"vesper"}}
  using Resend;

  IResend resend = ResendClient.Create( "re_xxxxxxxxx" ); // Or from DI

  var resp = await resend.EmailSendAsync( new EmailMessage()
  {
      From = "Acme <onboarding@resend.dev>",
      To = "delivered@resend.dev",
      Subject = "hello world",
      HtmlBody = "<p>it works!</p>",
      ReplyTo = "onboarding@resend.dev",
      Tags = new List<EmailTag> { new EmailTag { Name = "category", Value = "confirm_email" } }
  } );
  Console.WriteLine( "Email Id={0}", resp.Content );
  ```

  ```bash cURL {9-14} theme={"theme":{"light":"github-light","dark":"vesper"}}
  curl -X POST 'https://api.resend.com/emails' \
       -H 'Authorization: Bearer re_xxxxxxxxx' \
       -H 'Content-Type: application/json' \
       -d $'{
    "from": "Acme <onboarding@resend.dev>",
    "to": ["delivered@resend.dev"],
    "subject": "hello world",
    "html": "<p>it works!</p>",
    "tags": [
      {
        "name": "category",
        "value": "confirm_email"
      }
    ]
  }'
  ```
</CodeGroup>

## Add tags on the `POST /emails/batch` endpoint

<CodeGroup>
  ```ts Node.js {11-16,23-28} theme={"theme":{"light":"github-light","dark":"vesper"}}
  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',
        },
      ],
    },
  ]);
  ```

  ```php PHP {9-13,21-25} theme={"theme":{"light":"github-light","dark":"vesper"}}
  $resend = Resend::client('re_xxxxxxxxx');

  $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'
        ]
      ]
    ]
  ]);
  ```

  ```py Python {12-17,24-29} theme={"theme":{"light":"github-light","dark":"vesper"}}
  import resend
  from typing import List

  resend.api_key = "re_xxxxxxxxx"

  params: List[resend.Emails.SendParams] = [
    {
      "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"
        }
      ]
    }
  ]

  resend.Batch.send(params)
  ```

  ```rb Ruby {11-16,23-28} theme={"theme":{"light":"github-light","dark":"vesper"}}
  require "resend"

  Resend.api_key = 're_xxxxxxxxx'

  params = [
    {
      "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"
        }
      ]
    }
  ]

  Resend::Batch.send(params)
  ```

  ```go Go {22,29} theme={"theme":{"light":"github-light","dark":"vesper"}}
  package main

  import (
  	"fmt"
  	"os"

  	"github.com/resend/resend-go/v3"
  )

  func main() {

    ctx := context.TODO()

    client := resend.NewClient("re_xxxxxxxxx")

    var batchEmails = []*resend.SendEmailRequest{
      {
        From:    "Acme <onboarding@resend.dev>",
        To:      []string{"foo@gmail.com"},
        Subject: "hello world",
        Html:    "<h1>it works!</h1>",
        Tags:    []resend.Tag{{Name: "category", Value: "confirm_email"}},
      },
      {
        From:    "Acme <onboarding@resend.dev>",
        To:      []string{"bar@outlook.com"},
        Subject: "world hello",
        Html:    "<p>it works!</p>",
        Tags:    []resend.Tag{{Name: "category", Value: "confirm_email"}},
      },
    }

    sent, err := client.Batch.SendWithContext(ctx, batchEmails)

    if err != nil {
      panic(err)
    }
    fmt.Println(sent.Data)
  }
  ```

  ```rust Rust {15,22} theme={"theme":{"light":"github-light","dark":"vesper"}}
  use resend_rs::types::CreateEmailBaseOptions;
  use resend_rs::{Resend, Result};

  #[tokio::main]
  async fn main() -> Result<()> {
    let resend = Resend::new("re_xxxxxxxxx");

    let emails = vec![
      CreateEmailBaseOptions::new(
        "Acme <onboarding@resend.dev>",
        vec!["foo@gmail.com"],
        "hello world",
      )
      .with_html("<h1>it works!</h1>")
      .with_tag(Tag::new("category", "confirm_email")),
      CreateEmailBaseOptions::new(
        "Acme <onboarding@resend.dev>",
        vec!["bar@outlook.com"],
        "world hello",
      )
      .with_html("<p>it works!</p>")
      .with_tag(Tag::new("category", "confirm_email")),
    ];

    let _emails = resend.batch.send(emails).await?;

    Ok(())
  }
  ```

  ```java Java {12-15,23-26} theme={"theme":{"light":"github-light","dark":"vesper"}}
  import com.resend.*;

  public class Main {
      public static void main(String[] args) {
          Resend resend = new Resend("re_xxxxxxxxx");

          CreateEmailOptions firstEmail = CreateEmailOptions.builder()
              .from("Acme <onboarding@resend.dev>")
              .to("foo@gmail.com")
              .subject("hello world")
              .html("<h1>it works!</h1>")
              .tags(Tag.builder()
                  .name("category")
                  .value("confirm_email")
                  .build())
              .build();

          CreateEmailOptions secondEmail = CreateEmailOptions.builder()
              .from("Acme <onboarding@resend.dev>")
              .to("bar@outlook.com")
              .subject("world hello")
              .html("<p>it works!</p>")
              .tags(Tag.builder()
                  .name("category")
                  .value("confirm_email")
                  .build())
              .build();

          CreateBatchEmailsResponse data = resend.batch().send(
              Arrays.asList(firstEmail, secondEmail)
          );
      }
  }
  ```

  ```csharp .NET {11,20} theme={"theme":{"light":"github-light","dark":"vesper"}}
  using Resend;

  IResend resend = ResendClient.Create( "re_xxxxxxxxx" ); // Or from DI

  var mail1 = new EmailMessage()
  {
      From = "Acme <onboarding@resend.dev>",
      To = "foo@gmail.com",
      Subject = "hello world",
      HtmlBody = "<p>it works!</p>",
      Tags = new List<EmailTag> { new EmailTag { Name = "category", Value = "confirm_email" } }
  };

  var mail2 = new EmailMessage()
  {
      From = "Acme <onboarding@resend.dev>",
      To = "bar@outlook.com",
      Subject = "hello world",
      HtmlBody = "<p>it works!</p>",
      Tags = new List<EmailTag> { new EmailTag { Name = "category", Value = "confirm_email" } }
  };

  var resp = await resend.EmailBatchAsync( [ mail1, mail2 ] );
  Console.WriteLine( "Nr Emails={0}", resp.Content.Count );
  ```

  ```bash cURL {10-15,22-27} theme={"theme":{"light":"github-light","dark":"vesper"}}
  curl -X POST 'https://api.resend.com/emails/batch' \
       -H 'Authorization: Bearer re_xxxxxxxxx' \
       -H 'Content-Type: application/json' \
       -d $'[
    {
      "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"
        }
      ]
    }
  ]'
  ```
</CodeGroup>