> ## 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.

# Open and Click Tracking

> Track open and click rates of your emails.

Open and click tracking is disabled by default for all domains.

You can enable it manually or programmatically. Once verified, all tracked links in your emails will use your tracking subdomain (e.g., `links.emails.example.com`).

<Tabs>
  <Tab title="Using the dashboard">
    Go to the [**Domains** page](https://resend.com/domains) and click on the domain you want to configure.

    In the **Configuration** tab, click **Configure** under **Enable tracking metrics**.

    <img alt="Open and Click Tracking" src="https://mintcdn.com/resend/8slja5cHAobSwGo7/images/dashboard-domains-custom-tracking-domains.png?fit=max&auto=format&n=8slja5cHAobSwGo7&q=85&s=b94c649f1c22c899c144cd73ab5a8e73" width="1869" height="959" data-path="images/dashboard-domains-custom-tracking-domains.png" />

    Provide a name for your tracking subdomain, enable open and/or click tracking, and click **+Add domain**.

    <img alt="Verify Custom Tracking Subdomain" src="https://mintcdn.com/resend/aVe4W1upaT_ALaEY/images/dashboard-custom-tracking-domain-verify.png?fit=max&auto=format&n=aVe4W1upaT_ALaEY&q=85&s=aac30239e34f1fbf89bb9e41ba5540e8" width="3360" height="2100" data-path="images/dashboard-custom-tracking-domain-verify.png" />

    Add the CNAME record to your DNS settings (e.g. Cloudflare, GoDaddy, etc.) to verify your tracking subdomain.

    <img alt="Add Custom Tracking Subdomain" src="https://mintcdn.com/resend/aVe4W1upaT_ALaEY/images/dashboard-domains-custom-tracking-domains-add.png?fit=max&auto=format&n=aVe4W1upaT_ALaEY&q=85&s=118b4d5f8269265c5eed074a52a2c9e5" width="3776" height="2096" data-path="images/dashboard-domains-custom-tracking-domains-add.png" />

    <Info>
      If we detect CAA records on your domain, we will show an additional CAA record
      that needs to be created. This ensures that we can issue a TLS certificate for
      your tracking subdomain.
    </Info>

    Click **I've added the records** to verify the domain.

    Once verified, all tracked links in your emails will use your custom tracking subdomain.
  </Tab>

  <Tab title="Using the API">
    You can add a tracking subdomain when creating a new domain by passing the `tracking_subdomain` field along with `click_tracking` and/or `open_tracking`.

    <CodeGroup>
      ```ts Node.js theme={"theme":{"light":"github-light","dark":"vesper"}}
      import { Resend } from 'resend';

      const resend = new Resend('re_xxxxxxxxx');

      const { data, error } = await resend.domains.create({
        name: 'example.com',
        openTracking: true,
        clickTracking: true,
        trackingSubdomain: 'links',
      });
      ```

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

      $resend->domains->create([
        'name' => 'example.com',
        'open_tracking' => true,
        'click_tracking' => true,
        'tracking_subdomain' => 'links',
      ]);
      ```

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

      resend.api_key = "re_xxxxxxxxx"

      params: resend.Domains.CreateParams = {
        "name": "example.com",
        "open_tracking": True,
        "click_tracking": True,
        "tracking_subdomain": "links",
      }

      resend.Domains.create(params)
      ```

      ```ruby Ruby theme={"theme":{"light":"github-light","dark":"vesper"}}
      Resend.api_key = "re_xxxxxxxxx"

      params = {
        name: "example.com",
        open_tracking: true,
        click_tracking: true,
        tracking_subdomain: "links",
      }
      Resend::Domains.create(params)
      ```

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

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

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

      	params := &resend.CreateDomainRequest{
      		Name:              "example.com",
      		OpenTracking:      true,
      		ClickTracking:     true,
      		TrackingSubdomain: "links",
      	}

      	client.Domains.Create(params)
      }
      ```

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

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

        let _domain = resend
          .domains
          .create(
            CreateDomainOptions::new("example.com")
              .with_open_tracking(true)
              .with_click_tracking(true)
              .with_tracking_subdomain("links"),
          )
          .await?;

        Ok(())
      }
      ```

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

      Resend resend = new Resend("re_xxxxxxxxx");

      CreateDomainOptions params = CreateDomainOptions.builder()
              .name("example.com")
              .openTracking(true)
              .clickTracking(true)
              .trackingSubdomain("links")
              .build();

      resend.domains().create(params);
      ```

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

      IResend resend = ResendClient.Create( "re_xxxxxxxxx" );

      var resp = await resend.DomainAddAsync( new DomainAddData()
      {
          DomainName = "example.com",
          OpenTracking = true,
          ClickTracking = true,
          TrackingSubdomain = "links",
      } );
      ```

      ```bash cURL theme={"theme":{"light":"github-light","dark":"vesper"}}
      curl -X POST 'https://api.resend.com/domains' \
           -H 'Authorization: Bearer re_xxxxxxxxx' \
           -H 'Content-Type: application/json' \
           -d $'{
        "name": "example.com",
        "open_tracking": true,
        "click_tracking": true,
        "tracking_subdomain": "links"
      }'
      ```
    </CodeGroup>

    If you already have a domain, you can call the `update` endpoint to add a tracking subdomain and enable tracking.

    <CodeGroup>
      ```ts Node.js theme={"theme":{"light":"github-light","dark":"vesper"}}
      import { Resend } from 'resend';

      const resend = new Resend('re_xxxxxxxxx');

      const { data, error } = await resend.domains.update({
        id: 'd91cd9bd-1176-453e-8fc1-35364d380206',
        openTracking: true,
        clickTracking: true,
        trackingSubdomain: 'links',
      });
      ```

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

      $resend->domains->update(
        'd91cd9bd-1176-453e-8fc1-35364d380206',
        [
          'open_tracking' => true,
          'click_tracking' => true,
          'tracking_subdomain' => 'links',
        ]
      );
      ```

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

      resend.api_key = "re_xxxxxxxxx"

      params: resend.Domains.UpdateParams = {
        "id": "d91cd9bd-1176-453e-8fc1-35364d380206",
        "open_tracking": True,
        "click_tracking": True,
        "tracking_subdomain": "links",
      }

      resend.Domains.update(params)
      ```

      ```ruby Ruby theme={"theme":{"light":"github-light","dark":"vesper"}}
      Resend.api_key = "re_xxxxxxxxx"

      Resend::Domains.update({
        id: "d91cd9bd-1176-453e-8fc1-35364d380206",
        open_tracking: true,
        click_tracking: true,
        tracking_subdomain: "links",
      })
      ```

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

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

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

      	params := &resend.UpdateDomainRequest{
      		OpenTracking:      true,
      		ClickTracking:     true,
      		TrackingSubdomain: "links",
      	}

      	client.Domains.Update("d91cd9bd-1176-453e-8fc1-35364d380206", params)
      }
      ```

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

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

        let changes = DomainChanges::new()
          .with_open_tracking(true)
          .with_click_tracking(true)
          .with_tracking_subdomain("links");

        let _domain = resend
          .domains
          .update("d91cd9bd-1176-453e-8fc1-35364d380206", changes)
          .await?;

        Ok(())
      }
      ```

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

      Resend resend = new Resend("re_xxxxxxxxx");

      UpdateDomainOptions params = UpdateDomainOptions.builder()
              .id("d91cd9bd-1176-453e-8fc1-35364d380206")
              .openTracking(true)
              .clickTracking(true)
              .trackingSubdomain("links")
              .build();

      resend.domains().update(params);
      ```

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

      IResend resend = ResendClient.Create( "re_xxxxxxxxx" );

      await resend.DomainUpdateAsync(
          new Guid( "d91cd9bd-1176-453e-8fc1-35364d380206" ),
          new DomainUpdateData()
          {
              TrackOpen = true,
              TrackClicks = true,
              TrackingSubdomain = "links",
          }
      );
      ```

      ```bash cURL theme={"theme":{"light":"github-light","dark":"vesper"}}
      curl -X PATCH 'https://api.resend.com/domains/d91cd9bd-1176-453e-8fc1-35364d380206' \
           -H 'Authorization: Bearer re_xxxxxxxxx' \
           -H 'Content-Type: application/json' \
           -d $'{
        "open_tracking": true,
        "click_tracking": true,
        "tracking_subdomain": "links"
      }'
      ```
    </CodeGroup>

    Whether creating or updating a domain, the API will return the required DNS records that need to be added to your domain provider's DNS settings. Note the `Tracking` record.

    ```json {15-22} API Response Example theme={"theme":{"light":"github-light","dark":"vesper"}}
    {
      "id": "4dd369bc-aa82-4ff3-97de-514ae3000ee0",
      "name": "example.com",
      "created_at": "2026-03-28T17:12:02.059593+00:00",
      "status": "not_started",
      "open_tracking": true,
      "click_tracking": true,
      "tracking_subdomain": "links",
      "capabilities": {
        "sending": "enabled",
        "receiving": "disabled"
      },
      "records": [
        // ... other records ...
        {
          "record": "Tracking",
          "name": "links.example.com",
          "type": "CNAME",
          "value": "links1.resend-dns.com",
          "ttl": "Auto",
          "status": "not_started"
        }
      ],
      "region": "us-east-1"
    }
    ```

    Add the required `CNAME` record to your domain provider's DNS settings (e.g. Cloudflare, GoDaddy, etc.).

    <Info>
      If we detect CAA records on your domain, we will show an additional CAA record
      that needs to be created. This ensures that we can issue a TLS certificate for
      your tracking subdomain.
    </Info>

    Once you've added the required DNS record(s), call the `verify` endpoint to verify the domain.

    <CodeGroup>
      ```ts Node.js theme={"theme":{"light":"github-light","dark":"vesper"}}
      import { Resend } from 'resend';

      const resend = new Resend('re_xxxxxxxxx');

      const { data, error } = await resend.domains.verify(
        'd91cd9bd-1176-453e-8fc1-35364d380206',
      );
      ```

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

      $resend->domains->verify('d91cd9bd-1176-453e-8fc1-35364d380206');
      ```

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

      resend.api_key = "re_xxxxxxxxx"

      resend.Domains.verify(domain_id="d91cd9bd-1176-453e-8fc1-35364d380206")
      ```

      ```ruby Ruby theme={"theme":{"light":"github-light","dark":"vesper"}}
      Resend.api_key = "re_xxxxxxxxx"

      Resend::Domains.verify("d91cd9bd-1176-453e-8fc1-35364d380206")
      ```

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

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

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

      	client.Domains.Verify("d91cd9bd-1176-453e-8fc1-35364d380206")
      }
      ```

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

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

        resend
          .domains
          .verify("d91cd9bd-1176-453e-8fc1-35364d380206")
          .await?;

        Ok(())
      }
      ```

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

      Resend resend = new Resend("re_xxxxxxxxx");

      VerifyDomainResponse verified = resend.domains().verify("d91cd9bd-1176-453e-8fc1-35364d380206");
      ```

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

      IResend resend = ResendClient.Create( "re_xxxxxxxxx" );

      await resend.DomainVerifyAsync( new Guid( "d91cd9bd-1176-453e-8fc1-35364d380206" ) );
      ```

      ```bash cURL theme={"theme":{"light":"github-light","dark":"vesper"}}
      curl -X POST 'https://api.resend.com/domains/d91cd9bd-1176-453e-8fc1-35364d380206/verify' \
           -H 'Authorization: Bearer re_xxxxxxxxx' \
           -H 'Content-Type: application/json'
      ```
    </CodeGroup>

    <Note>
      Tracking is active only when both of these conditions are met:

      <ol>
        <li>
          The `open_tracking` or `click_tracking` setting is enabled for the domain.
        </li>

        <li>
          A tracking subdomain is configured (e.g., `links.example.com`) and
          successfully verified.
        </li>
      </ol>
    </Note>

    All tracked links in your emails will use your tracking subdomain.

    View the [API reference](/api-reference/domains/create-domain) for more details.
  </Tab>
</Tabs>

## How Open Tracking Works

A 1x1 pixel transparent GIF image is inserted in each email and includes a unique reference to this image file. When
the image is downloaded, Resend can tell exactly which message was opened and by whom.

## How Click Tracking Works

To track clicks, Resend modifies each link in the body of the HTML email to point to your tracking subdomain.

When recipients clicks a link, the request is redirected to your tracking subdomain, their click event is recorded, and they are redirected to the original URL.

## Troubleshooting

### Occasional Extra Verification Step

If we detect CAA records on your domain, we will show an additional CAA record that needs to be created. This ensures
that we can issue a TLS certificate for your tracking subdomain.

### Changing the Tracking Subdomain

Because tracking subdomains are used in email links, we handle them differently than other records.

* **Not removable**: After your tracking subdomain has been created, it can only be changed, never removed. This behavior preserves any
  email links that may already be sent with the current tracking subdomain. For this reason, do **not remove old tracking DNS records**. (All previously used records remain active and are included in the response.)
* **Requires verification**: After changing the tracking subdomain, a new DNS record must be verified. Until then, the previous value is used.
* **Update time limitations**: Changes are limited to once every 24 hours.

### Removing a Domain with a Tracking Subdomain

If you remove a domain with a configured tracking subdomain, the Resend provisioned proxy will also be removed, breaking
any existing email links that use that subdomain.

To keep links working, set up your own proxy pointing to Resend’s tracking DNS records before removing the domain.

### Unsupported Domains

Custom tracking subdomains require us to issue a TLS certificate. Some domains under regional restrictions are not
supported by our certificate provider and cannot use custom tracking subdomains. Learn more in the [certificate provider
docs](https://knowledge.digicert.com/solution/embargoed-countries-and-regions).