Domains and Redirects

A domain name is the web address or URL used to visit your site. The Domain Name System (DNS) resolves human-readable names like www.example.com into machine-readable IP addresses like 127.0.0.1. All Pantheon sites are accessible via platform domains, and you can easily connect your own custom domain to paid sites.

Platform Domains

Pantheon issues platform domains for all environments. Each environment (Dev, Test, Live, each Multidev) is accessible via the platform domain, matching the following patterns:

• dev-site-name.pantheonsite.io
• test-site-name.pantheonsite.io
• live-site-name.pantheonsite.io
• multidev-env-site-name.pantheonsite.io

All platform domains are available over HTTPS. Redirecting to HTTPS during development and testing is a good best practice to ensure you are ready to go live with HTTPS.

robots.txt

Pantheon serves a default robots.txt that disallows crawlers on platform domains (/*.pantheonsite.io, /*.pantheon.io, /*.gotpantheon.com, and /*.sites.my-agency.com). Crawlers are allowed on the Live environment for requests served with a custom domain (e.g., www.example.com). If you attempt to access your Live environment with a platform domain, even if you have a domain associated with the environment, the default robots.txt will be served.

Pantheon does not allow crawlers on Dev, Test, or Multidev environments. Adding a custom domain to an environment other than Live will not permit crawlers to that environment.

Custom Domains

If you don't already own a domain name, register one with a third-party provider. Pantheon is not a domain registrar. Connect your custom domain on the Site Dashboard, and point DNS at Pantheon to trigger automated HTTPS provisioning.

A paid plan is required to connect custom domains to your site, up to the following limits:

Configure DNS

A custom domain requires specific DNS configurations to handle requests for your Pantheon site. We recommend configuring the following record types wherever you host DNS services for the domain:

• CNAME
• A
• AAAA (2)

Some DNS service providers do not support AAAA records, which are used to map IPv6 addresses. IPv6 offers security benefits and performance gains, especially for mobile users. This is largely because the new protocol is capable of carrying larger packets, resulting in fewer roundtrips per request. We strongly recommend transferring DNS services to a provider that supports IPv6 in order to take advantage of these benefits.

Some DNS service providers require expanded AAAA records. You can retrieve the expanded version for each AAAA record by using the IPv6 conversion tool and copying the "IPv6 longest" result.

For details on what values to use when configuring DNS, refer to Launch Essentials.

Nameservers

Pantheon does not host DNS zones or provide nameserver records. Many other platforms and hosting providers offer DNS servers and while it's convenient, it's often inflexible. Providers that offer nameservers usually build other features (like HTTPS) in a way that will only work for customers who use the provided nameservers. This approach is fine until it interferes with more advanced deployments.

Primary Domain

Pantheon uses the term primary domain to refer to a single domain used to serve all traffic from a site. For example, configuring www.example.com as the primary domain means that requests to example.com (or any other domain connected to the environment) all get redirected to www.example.com.

Redirecting all traffic to a primary domain is a best practice for SEO since it avoids duplicate content. It also prevents session strangeness, where a user can be logged in to one domain but logged out of other domains at the same time, and it can make it easier to measure and monitor website traffic.

Redirect to HTTPS and the Primary Domain

It's a best practice for SEO and security to standardize all traffic on HTTPS and choose a primary domain. Configure redirects to the primary domain with HTTPS in settings.php or wp-config.php:

• WordPress
• Drupal 8
• Drupal 7

if (isset($_ENV['PANTHEON_ENVIRONMENT']) && php_sapi_name() != 'cli') {
  // Redirect to https://$primary_domain in the Live environment
  if ($_ENV['PANTHEON_ENVIRONMENT'] === 'live') {
    /** Replace www.example.com with your registered domain name */
    $primary_domain = 'www.example.com';
  }
  else {
    // Redirect to HTTPS on every Pantheon environment.
    $primary_domain = $_SERVER['HTTP_HOST'];
  }

  if ($_SERVER['HTTP_HOST'] != $primary_domain
      || !isset($_SERVER['HTTP_USER_AGENT_HTTPS'])
      || $_SERVER['HTTP_USER_AGENT_HTTPS'] != 'ON' ) {

    # Name transaction "redirect" in New Relic for improved reporting (optional)
    if (extension_loaded('newrelic')) {
      newrelic_name_transaction("redirect");
    }

    header('HTTP/1.0 301 Moved Permanently');
    header('Location: https://'. $primary_domain . $_SERVER['REQUEST_URI']);
    exit();
  }
}

if (isset($_ENV['PANTHEON_ENVIRONMENT']) && php_sapi_name() != 'cli') {
  // Redirect to https://$primary_domain in the Live environment
  if ($_ENV['PANTHEON_ENVIRONMENT'] === 'live') {
    /** Replace www.example.com with your registered domain name */
    $primary_domain = 'www.example.com';
  }
  else {
    // Redirect to HTTPS on every Pantheon environment.
    $primary_domain = $_SERVER['HTTP_HOST'];
  }

  if ($_SERVER['HTTP_HOST'] != $primary_domain
      || !isset($_SERVER['HTTP_USER_AGENT_HTTPS'])
      || $_SERVER['HTTP_USER_AGENT_HTTPS'] != 'ON' ) {

    # Name transaction "redirect" in New Relic for improved reporting (optional)
    if (extension_loaded('newrelic')) {
      newrelic_name_transaction("redirect");
    }

    header('HTTP/1.0 301 Moved Permanently');
    header('Location: https://'. $primary_domain . $_SERVER['REQUEST_URI']);
    exit();
  }
  // Drupal 8 Trusted Host Settings
  if (is_array($settings)) {
    $settings['trusted_host_patterns'] = array('^'. preg_quote($primary_domain) .'$');
  }
}

if (isset($_ENV['PANTHEON_ENVIRONMENT']) && php_sapi_name() != 'cli') {
  // Redirect to https://$primary_domain in the Live environment
  if ($_ENV['PANTHEON_ENVIRONMENT'] === 'live') {
    /** Replace www.example.com with your registered domain name */
    $primary_domain = 'www.example.com';
  }
  else {
    // Redirect to HTTPS on every Pantheon environment.
    $primary_domain = $_SERVER['HTTP_HOST'];
  }

  if ($_SERVER['HTTP_HOST'] != $primary_domain
      || !isset($_SERVER['HTTP_USER_AGENT_HTTPS'])
      || $_SERVER['HTTP_USER_AGENT_HTTPS'] != 'ON' ) {

    # Name transaction "redirect" in New Relic for improved reporting (optional)
    if (extension_loaded('newrelic')) {
      newrelic_name_transaction("redirect");
    }

    header('HTTP/1.0 301 Moved Permanently');
    header('Location: https://'. $primary_domain . $_SERVER['REQUEST_URI']);
    exit();
  }
}

// Require HTTPS.
if (isset($_SERVER['PANTHEON_ENVIRONMENT']) &&
   ($_SERVER['HTTPS'] === 'OFF') &&
   // Check if Drupal or WordPress is running via command line
   (php_sapi_name() != "cli")) {
   if (!isset($_SERVER['HTTP_USER_AGENT_HTTPS']) ||
   (isset($_SERVER['HTTP_USER_AGENT_HTTPS']) && $_SERVER['HTTP_USER_AGENT_HTTPS'] != 'ON')) {
     header('HTTP/1.0 301 Moved Permanently');
     header('Location: https://'. $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI']);
     exit();

    # Name transaction "redirect" in New Relic for improved reporting (optional)
    if (extension_loaded('newrelic')) {
      newrelic_name_transaction("redirect");
    }
 }
}

// Redirect subdomain to a specific path.
if (isset($_ENV['PANTHEON_ENVIRONMENT']) &&
($_SERVER['HTTP_HOST'] == 'subdomain.example.com') &&
// Check if Drupal or WordPress is running via command line
(php_sapi_name() != "cli")) {
$newurl = 'https://www.example.com/subdirectory/'. $_SERVER['REQUEST_URI'];
header('HTTP/1.0 301 Moved Permanently');
header("Location: $newurl");
exit();
}

// 301 Redirect from /old to /new
// Check if Drupal or WordPress is running via command line
if (($_SERVER['REQUEST_URI'] == '/old') && (php_sapi_name() != "cli")) {
    header('HTTP/1.0 301 Moved Permanently');
    header('Location: https://'. $_SERVER['HTTP_HOST'] . '/new');
    exit();
}

$redirects = array(
"/",
"/old",
"/another/path",
"/old-path");

// 301 Redirect from multiple paths
// Check if Drupal or WordPress is running via command line
if ((in_array($_SERVER['REQUEST_URI'], $redirects)) && (php_sapi_name() != "cli")) {
header('HTTP/1.0 301 Moved Permanently');
header('Location: https://'. $_SERVER['HTTP_HOST'] . '/new-path-for-all');
exit();
}

// Redirect multiple subdomains to a single domain.
if (isset($_ENV['PANTHEON_ENVIRONMENT']) &&
  ($_ENV['PANTHEON_ENVIRONMENT'] === 'live') &&
// Check if Drupal or WordPress is running via command line
(php_sapi_name() != "cli")) {
  if (in_array($_SERVER['HTTP_HOST'], array(
    'sub1.example.com',
    'sub2.example.com',
    'sub3.example.com',
    'sub4.example.com'
  ))) {
    header('HTTP/1.0 301 Moved Permanently');
    header('Location: https://new.example.com'. $_SERVER['REQUEST_URI']);
    exit();
  }
}

$request_parts = explode('/', $_SERVER['REQUEST_URI']);
$legacy_username = $legacy_path = '';
if (isset($request_parts[1]) && strpos($request_parts[1], '~') === 0) {
$legacy_username = substr($request_parts[1], 1);
// If FALSE, then the request was just to the username.
$legacy_path = substr($_SERVER['REQUEST_URI'], (strlen($request_parts[1]) + 1));
}
if ($legacy_username) {
// Your custom logic.
}

Vanity Domains for Organizations

Pantheon Partners, Strategic Partners, Enterprise accounts, Resellers, and OEM Partners have the ability to provision a custom vanity domain for each environment on every site running on the platform, in addition to the default platform domain (pantheonsite.io).

For details, see Vanity Domains.

Troubleshooting

Failed cache clears, search and replace, or Drush and WP-CLI operations

All redirect logic should include the php_sapi_name() != "cli" conditional statement to see if WordPress or Drupal is running via the command line. Drush and WP-CLI are used by the platform for operations like cache clearing and search and replace, so it is important to only redirect web requests, otherwise the redirect will kill the PHP process before Drush or WP-CLI is executed, resulting in a silent failure:

[notice] Command: <site>.<env> -- 'drush <command>' [Exit: 1]
[error]

Infinite Redirect Loops

Errors referencing too many redirects may be a result of using the $_SERVER['HTTP_X_FORWARDED_PROTO'] variable within redirect logic located in your site's wp-config.php or settings.php file. Resolve this error by replacing the offending redirect logic with the recommended code samples in the above section and for your specific use case.

Mixed-mode Browser Warnings

Replace http:// in the site's database and configure your CMS to assume users are visiting via HTTPS and the site’s primary domain. Templates for example should reference HTTPS in absolute CSS and Javascript sources, even when accessed with HTTP.

CNAME Record Workaround

If your domain's DNS configuration relies on an existing MX or TXT record that intentionally disallows CNAME records, you'll need to use A and AAAA records to configure DNS for subdomains (e.g., www.example.com) instead of CNAMEs.

1. Identify required A record value by querying the target environment's platform domain using a free online tool, such as https://www.whatsmydns.net/#A/live-example.pantheonsite.io

2. Do the same for the required AAAA values. For example, https://www.whatsmydns.net/#AAAA/live-example.pantheonsite.io

3. Log in to your DNS host and create two AAAA records and one A record for the desired subdomain (e.g., www) using the values returned in the steps above.

See Also

• Switching DNS From One Pantheon Site to Another