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Last Reviewed: March 16, 2022

Pantheon YAML Configuration Files

Learn how to manage advanced site configuration

Hook into platform workflows and manage advanced site configuration via the pantheon.yml file. Add it to the root of your site's codebase, and deploy it along with the rest of your code.

Create a pantheon.yml File

If a pantheon.yml file is not already present in the root of your site's code repository, you can create one by following the configuration steps outlined below.

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Find Your pantheon.yml File

Your site's pantheon.yml configuration file can be found in the root of your site's code repository. If you have a local git clone of your site, this is the project root. When accessing the site over an SFTP connection, look in the code directory.

Configure Your Site's pantheon.yml File

Review each of the sections below to make sure that you create and configure your pantheon.yml file correctly.

For reference implementations see example.pantheon.yml and Quicksilver Example Scripts.

Add api_version

The first step in creating your pantheon.yml file is to define the api_version .

Required Step

The api_version property is required for the pantheon.yml file to be valid.

api_version: 1

Protected Web Paths

Protect files and directories inside of your docroot from public web access with protected_web_paths. For example, the following ensures that a visitor to or receives Access Denied (403):

  - /example.txt
  - /example_directory

The pantheon.upstream.yml file provided by your upstream might define protected web paths. If it does, all of the paths listed in the upstream and all of the paths listed in your pantheon.yml file will be protected. If you wish to remove protection from any path listed in the upstream, set the protected_web_paths_override property.


  • Specify the exact path; path is case-sensitive
  • No regex or wildcards allowed
  • Paths begin with a leading / and are relative to your docroot
  • Limited to 24 protected paths
  • You may not be able to protect files or paths with special characters
  • Wait a few seconds for changes to take effect

Protected Web Paths Override

To disable all of the protected web paths defined by your site's upstream and all protected paths defined by the Pantheon platform, set the protected_web_paths_override property to true:

protected_web_paths_override: true


The standard protected web paths can be important to the security of your site. If you override protection with this property, be sure to copy all of the standard protected web paths into your pantheon.yml file, and only remove those that you are certain are safe to expose.

For a list of standard protected paths, see the pantheon.upstream.yml for:

Enforce HTTPS + HSTS

HTTPS adds a layer of encryption that prevents others from seeing or tampering with traffic to your site. HTTP Strict Transport Security (HSTS) instructs browsers to only connect via HTTPS and helps protect websites against protocol downgrade attacks and cookie hijacking.

Pantheon sites (using the default Pantheon upstreams) created or updated on or after September 30, 2019 default to enforcing HTTPS via a redirect and a short, 5-minute duration, HSTS header. You can override the default with the enforce_https directive in a site-specific pantheon.yml file.


Before adjusting enforce_https, review and understand the configuration options and all considerations to avoid unintended consequences.

If you use a plugin or module to set your HSTS header, it will create a duplicate header. Disable enforce_https in pantheon.yml to avoid an invalid policy.

Use of the HSTS header is defined by the enforce_https directive, and takes five possible values which are handled by Pantheon as shown below:

offDisabledNot set by Pantheon
transitional (default)Enforcedmax-age=300

For example, to set enforce_https as off:

enforce_https: off


  • Use of full or full+subdomains should be treated as a commitment. HSTS headers are cached by browsers for the duration of the max-age period. If your site is unable to serve HTTPS (for example, by moving to a host that doesn't support HTTPS), visitors will be unable to access your site.
  • Any option with +subdomains should only be used if you want to enforce HTTPS for all subdomains, even those not connected to Pantheon.
  • To prepare your site to serve all content via HTTPS, follow the Switching Sites from HTTP to HTTPS doc.

Test Your Site's HSTS Configuration for an A+ Rating

SSL Labs provides a free, online service that you can use to test your site's configuration. In order to obtain an A+ rating, a long-duration HSTS header using the full or full+subdomains value is required.

  1. Select a short-duration HSTS header (transitional or transitional+subdomains) to test your configuration before committing to the long-duration HSTS header.

  2. Send the long-duration HSTS header by moving to full or full+subdomains after you confirm that the HSTS works as expected in the Live environment.

Nested Docroot

Nest your docroot one level beneath your code repository in a directory named web:

web_docroot: true

The name of the nested directory is not configurable.

For more information, see Serving Sites from the Web Subdirectory.

Integrated Composer Build Step

You can enable or disable Integrated Composer in the pantheon.yml file. For example, to enable Integrated Composer:

build_step: true

Refer to Integrated Composer for more information.

PHP Version

Override the upstream's default PHP version with the php_version property. PHP version is managed in version control and deployed along with the rest of your site's code to encourage testing before making a change on your Live site.

For example, to override the upstream default value at the site level to PHP 8:

php_version: 8.0


  • Upgrading PHP Versions may require you to resolve compatibility issues with your site's codebase.
  • From time to time, we will roll out a new default version of PHP, which will be available to apply as a one-click update in the Dashboard. If you are overriding the default, make sure to remove php_version from pantheon.yml as soon as possible to ensure you don't miss the latest recommended PHP version.
  • You'll always be able to test new default PHP version in Dev and Test before deploying Live.

Specify a Version of MariaDB

Last reviewed: Mar 17 2022

Specify the site's version of MariaDB to keep the software your site uses current and up to date, or set a specific version to avoid incompatibilities:

  1. Enable automated backups and confirm that a backup has been created before you configure the database version.

  2. Push the changes to a Multidev and ensure that the site performs as expected.

Apply this change to an existing environment. If you try to create a new environment with the database key specified in pantheon.yml, the commit will be rejected with an error.

  1. Use the database directive in pantheon.yml to choose a specific version of MariaDB:
  version: 10.6

This can also be accomplished via one-click updates in the Site Dashboard.

  1. Confirm that the database upgrade completed successfully:

    • Using Terminus (recommended):

      echo "SELECT @@version;" | $(terminus connection:info $SITE.$ENV --fields=mysql_command --format=string)
    • From the Site Dashboard, find the Workflows dropdown on the Site Dashboard and confirm that the Workflows completed successfully.

    Keep in mind that some versions of Drupal and WordPress require a specific minimum or maximum version for compatibility.

This table shows the supported MariaDB version for each CMS:

CMSSupported MariaDB Version(s)
Drupal < 7.7610.3
Drupal ≥ 7.7610.4
Drupal < 8.510.3
Drupal ≥ 8.610.4
Drupal ≥ 9.010.4 or 10.6
WordPress10.4 or 10.6

Users of Drupal 6 sites should consider upgrading to the latest version of Drupal for better support.

Considerations - Drupal

The default database version for new sites is MariaDB 10.4.

If your site has any older contrib modules that are not compatible with MariaDB 10.4, set the MariaDB version of the new site to 10.3 in your pantheon.yml file.

The latest version of Drupal requires MariaDB 10.3 or later. If you have a site that you plan to upgrade, confirm that the database has been upgraded to MariaDB 10.3 or 10.4 in all environments before you begin the upgrade.

Confirm that the database upgrade completed successfully using the steps at the beginning of Specify a Version of MariaDB.

Considerations - InnoDB Row Size Too Large

MariaDB 10.4 on Pantheon has innodb_strict_mode set to ON. This leads to Row size too large errors that are not present on earlier versions of MariaDB:

returned non-zero exit status 1: ERROR 1118 (42000) at line 1296: Row size too large (> 8126). Changing some columns to TEXT or BLOB may help. In current row format, BLOB prefix of 0 bytes is stored inline.

Before you push the change to pantheon.yml to upgrade MariaDB to 10.4, modify your tables to use row_format=DYNAMIC to avoid Row size too large errors:

How to update all tables to row_format=DYNAMIC
  1. Log in with Terminus and find the site UUID:

    terminus auth:login --email <email>
    terminus site:list
  2. Optionally, set the UUID from step 1 as the local alias (replace site-uuid in this example):

    export SITE=site-uuid
  3. Run a SQL command to set ROW_FORMAT=DYNAMIC. Replace $ENV with the Multidev or environment, and $SITE with the site UUID:

    echo "SELECT CONCAT('ALTER TABLE \`', table_name, '\` ROW_FORMAT=DYNAMIC;') AS aQuery FROM information_schema.tables WHERE table_schema = 'pantheon';" | $(terminus connection:info $SITE.$ENV --fields=mysql_command --format=string) | grep -vE 'aQuery|_pt_heartbeat|_pantheon_heartbeat' | $(terminus connection:info $SITE.$ENV --fields=mysql_command --format=string)

For more information on how to diagnose tables and troubleshoot potential issues, refer to the official MariaDB documentation.

Specify a Redis Version

There are two available versions of Redis available for the Object Cache: 2.8 and 6.2. The default version for the platform is 2.8 currently.

Change the Redis Version

  1. Add the following block to your pantheon.yml file:

      version: 6.2
  2. Push the change.

Rollback the Redis Version

  1. Change the value of version to 2.8
  2. Push the change.

Test the Redis 6 Update

We recommend that you push the Redis version change to a Multidev environment:

  1. Create a new Multidev environment. Refer to Multidev Environmentfor more information.

  2. Push the pantheon.yml Redis change to the branch associated with the Multidev environment.

  3. Wait for the upgrade workflow to complete.

  4. Confirm the Redis version upgrade using redis-cli.

    • Get the redis-cli connection string from the “Connection Info” button on the Pantheon Dashboard for your Multidev environment.
  5. Connect to the Redis container with redis-cli.

  6. Type INFO Server when you are connected and verify that the redis_versionis correct.

Specify a Solr Version

Before you install the Drupal search module, you need to specify the Solr version or set a specific version to avoid incompatibilities. Specify Solr 8 as the search index for Drupal sites:

  version: 8


  • The valid values for the versions are 3 and 8.
  • Currently, Solr 8 is only supported for Drupal 9 and higher sites.

Drush Version

Add drush_version to the top level of the pantheon.yml file to configure the Drush version used when making calls remotely on Pantheon:

drush_version: 8

For more information and compatibility requirements, see Managing Drush Versions on Pantheon.

Filemount Path

Pantheon provides a cloud-based filesystem to store user-generated content and other website files. By default, we create a symlink to this filesystem at sites/default/files (Drupal), wp-content/uploads (WordPress), or app/uploads (WordPress using Bedrock), but you can change the location with the filemount variable.


We recommend only changing this setting when needed for Custom Upstream Configurations in pantheon.upstream.yml. For most cases, you can create an additional symlink in your code base.

The only valid filemount path other than the default path for each CMS is /files relative to your docroot:

filemount: /files

Complete the following before deploying filemount (required):

  1. Reconfigure Drupal 7 or WordPress to use the new path

  2. Add path to the .gitignore file.

  3. Configure a private subdirectory of the new path within protected_web_paths.

Search and Replace for WordPress Multisite (Early Access)

You can enable search and replace on WordPress Multisites by adding the following to your pantheon.yml file:

search_replace: true

Running search and replace on a subdomain Multisite also requires configuring a sites.yml file. Refer to WordPress Multisite Search and Replace for more information.

Quicksilver Platform Integration Hooks

Use the pantheon.yml file to define scripts you want executed automatically when a particular workflow is triggered on Pantheon by you or a team member. For example, you can write a script to post a message to Slack whenever code is pushed to the Site Dashboard.

For more information, see Automate your Workflow with Quicksilver Platform Integration Hooks and check our growing set of Platform Integration guides demonstrating Quicksilver hooks.

Custom Upstream Configurations

Add a pantheon.upstream.yml file to your Workspace's Custom Upstream to set default configurations for all downstream sites. The same properties described above can be used in this file. In addition, it is also possible to define a deploy_product Quicksilver hook here; however other Quicksilver workflows are not supported.

This file should only be edited in the Custom Upstream repository where it is defined. Similarly, the Custom Upstream repository should not define a pantheon.yml file; it should place all configuration settings in the upstream file instead.

When the same configuration value is defined in both files, the value from pantheon.yml will override the value from pantheon.upstream.yml at the site-level.


First, verify the syntax of entries in the file. Refer to the examples above for exact syntax, or try running the contents of your pantheon.yml file through a YAML linter.

"Changes to pantheon.yml detected, but there was an error while processing it"

The Platform will automatically reject a commit that includes a pantheon.yml error. The error message will resemble:

remote: Changes to `pantheon.yml` detected, but there was an error while processing it:
remote: Version '2' is not a valid pantheon.yml version!
remote: Valid versions are: 1

While our parser will reject a pantheon.yml that is invalid, it won't necessarily give you the exact reason the file is invalid. Syntax errors are the most common reason for an invalid pantheon.yml file.

Why can’t I update the PHP version on my Multidev?

The PHP version changes automatically when you modify the pantheon.yml file of a site with a pre-existing Multidev. A PHP version change will not appear in a Multidev created after your pantheon.yml changes are made. To update your Multidev:

  1. Navigate to your pantheon.yml file.

  2. Modify your pantheon.yml file and re-commit to the Multidev.

    • It does not matter what change you make to the file. Any change- even a comment- will allow the Multidev to detect the configuration change. You will receive a notice indicating configuration changes have been detected and applied to the Multidev environment:
remote: Changes to `pantheon.yml` detected.
remote: Successfully applied `pantheon.yml` to the 'new-feature' environment.

Pantheon.yml changes aren't reflected when creating a new Multidev

Issue: Changes to your pantheon.yml file won't be reflected if you created a Git branch locally, made a change to the pantheon.yml file, and then pushed the branch, or used a CI pipeline to create a new Multidev.


You must do one of the following to ensure that your newly created Multidev has the pantheon.yml changes:

  • Re-commit your changes to the Multidev and/or pantheon.yml file
  • Push the pantheon.yml changes directly to the Dev (master branch) environment

Deploying Hotfixes

Changes made to pantheon.yml are not detected when deployed as a hotfix. Git tags created manually and pushed on the platform do not invoke all the processes that an actual deployment does. Pantheon standard workflow is done via the dashboard deploy or terminus env:deploy. As a workaround for hotfixes:

  1. Modify your pantheon.yml file in a development environment (for example add a code comment).

  2. Deploy the changes to production using the dashboard deploy or terminus env:deploy.

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