diff --git a/documentation/environment-resolver.md b/documentation/environment-resolver.md
index 3caf4b6..ec4a868 100644
--- a/documentation/environment-resolver.md
+++ b/documentation/environment-resolver.md
@@ -52,3 +52,32 @@ $environment = $service->getActiveEnvironment();
 // Failure will throw an InvalidArgumentException.
 $project = $service->getActiveProject();
 ```
+
+### Active project roles
+
+This can be used to determine what "roles" the currently active project has.
+
+See [\Drupal\helfi_api_base\Environment\ProjectRoleEnum](/src/Environment/ProjectRoleEnum.php) for available roles.
+
+```php
+/** @var \Drupal\helfi_api_base\Environment\ActiveProjectRoles $activeProjectRoles */
+$activeProjectRoles = \Drupal::service(\Drupal\helfi_api_base\Environment\ActiveProjectRoles::class);
+// A boolean indicating whether the current instance has the given role.
+$activeProjectRoles->hasRole(\Drupal\helfi_api_base\Environment\ProjectRoleEnum::Core);
+```
+
+#### Determine if the current instance is a "core" instance
+
+The instance is considered as "core" instance if the instance is a part of the main-navigation structure. Currently, this includes all Drupal instances under www.hel.fi domain.
+
+This can be used to conditionally run code only in core instances, such as enabling a module.
+
+```php
+/** @var \Drupal\helfi_api_base\Environment\ActiveProjectRoles $activeProjectRoles */
+$activeProjectRoles = \Drupal::service(\Drupal\helfi_api_base\Environment\ActiveProjectRoles::class);
+
+if ($activeProjectRoles->hasRole(\Drupal\helfi_api_base\Environment\ProjectRoleEnum::Core)) {
+  // Do something only in core instances.
+}
+```
+
diff --git a/helfi_api_base.services.yml b/helfi_api_base.services.yml
index ad4d726..3842e57 100644
--- a/helfi_api_base.services.yml
+++ b/helfi_api_base.services.yml
@@ -28,6 +28,7 @@ services:
   Drupal\helfi_api_base\EventSubscriber\DisableUserPasswordSubscriber: ~
   Drupal\helfi_api_base\Features\FeatureManager: ~
 
+  Drupal\helfi_api_base\Environment\ActiveProjectRoles: ~
   Drupal\helfi_api_base\Environment\EnvironmentResolverInterface: '@helfi_api_base.environment_resolver'
   Drupal\helfi_api_base\Environment\EnvironmentResolver: '@helfi_api_base.environment_resolver'
   helfi_api_base.environment_resolver:
diff --git a/src/Environment/ActiveProjectRoles.php b/src/Environment/ActiveProjectRoles.php
new file mode 100644
index 0000000..993ca71
--- /dev/null
+++ b/src/Environment/ActiveProjectRoles.php
@@ -0,0 +1,52 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\helfi_api_base\Environment;
+
+/**
+ * A service to determine the roles of currently active project.
+ */
+final class ActiveProjectRoles {
+
+  public function __construct(private readonly EnvironmentResolverInterface $environmentResolver) {
+  }
+
+  /**
+   * Checks if the current instance has the given role.
+   *
+   * @return bool
+   *   TRUE if the project has given role.
+   */
+  public function hasRole(ProjectRoleEnum $role): bool {
+    return in_array($role, $this->getRoles());
+  }
+
+  /**
+   * Gets the project features.
+   *
+   * @return array<\Drupal\helfi_api_base\Environment\ProjectRoleEnum>
+   *   The features.
+   */
+  private function getRoles(): array {
+    $roles = [];
+
+    try {
+      // Instance is considered as a "core" if it's included in main-navigation
+      // structure, so basically all Drupal instances under www.hel.fi domain.
+      //
+      // Currently, only core instances are defined in EnvironmentResolver, so
+      // we can use ::getActiveProject() to determine if the current instance is
+      // a core instance.
+      // @todo Include all instances in EnvironmentResolver and include
+      // Project role data in Project object.
+      $this->environmentResolver->getActiveProject();
+
+      $roles[] = ProjectRoleEnum::Core;
+    }
+    catch (\InvalidArgumentException) {
+    }
+    return $roles;
+  }
+
+}
diff --git a/src/Environment/EnvironmentTrait.php b/src/Environment/EnvironmentTrait.php
index cc6fd42..4ecb690 100644
--- a/src/Environment/EnvironmentTrait.php
+++ b/src/Environment/EnvironmentTrait.php
@@ -28,6 +28,8 @@ protected function normalizeEnvironmentName(string $environment) : ? string {
       'testing' => 'test',
       'staging' => 'stage',
       'production' => 'prod',
+      // Make sure CI resolves to a known environment.
+      'ci' => 'test',
     ];
 
     if (array_key_exists($environment, $environments)) {
diff --git a/src/Environment/ProjectRoleEnum.php b/src/Environment/ProjectRoleEnum.php
new file mode 100644
index 0000000..0a846b7
--- /dev/null
+++ b/src/Environment/ProjectRoleEnum.php
@@ -0,0 +1,12 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\helfi_api_base\Environment;
+
+/**
+ * Defines the project features.
+ */
+enum ProjectRoleEnum {
+  case Core;
+}
diff --git a/tests/src/Unit/Environment/ActiveProjectRolesTest.php b/tests/src/Unit/Environment/ActiveProjectRolesTest.php
new file mode 100644
index 0000000..8e481db
--- /dev/null
+++ b/tests/src/Unit/Environment/ActiveProjectRolesTest.php
@@ -0,0 +1,47 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\helfi_api_base\Unit\Environment;
+
+use Drupal\Tests\UnitTestCase;
+use Drupal\Tests\helfi_api_base\Traits\EnvironmentResolverTrait;
+use Drupal\helfi_api_base\Environment\ActiveProjectRoles;
+use Drupal\helfi_api_base\Environment\EnvironmentEnum;
+use Drupal\helfi_api_base\Environment\Project;
+use Drupal\helfi_api_base\Environment\ProjectRoleEnum;
+
+/**
+ * Tests ActiveProjectType.
+ *
+ * @group helfi_api_base
+ */
+class ActiveProjectRolesTest extends UnitTestCase {
+
+  use EnvironmentResolverTrait;
+
+  /**
+   * Tests ::isCoreInstance().
+   *
+   * @dataProvider isCoreInstanceData
+   */
+  public function testIsCoreInstance(bool $expected, ?string $projectName, ?EnvironmentEnum $env): void {
+    $sut = new ActiveProjectRoles($this->getEnvironmentResolver($projectName, $env));
+    $this->assertEquals($expected, $sut->hasRole(ProjectRoleEnum::Core));
+  }
+
+  /**
+   * A data provider.
+   *
+   * @return array[]
+   *   The data.
+   */
+  public function isCoreInstanceData(): array {
+    return [
+      [FALSE, NULL, NULL],
+      [TRUE, Project::ASUMINEN, EnvironmentEnum::Local],
+      [FALSE, 'non-existent', NULL],
+    ];
+  }
+
+}
diff --git a/tests/src/Unit/Environment/EnvironmentResolverTest.php b/tests/src/Unit/Environment/EnvironmentResolverTest.php
index 02f0d97..8acb7c5 100644
--- a/tests/src/Unit/Environment/EnvironmentResolverTest.php
+++ b/tests/src/Unit/Environment/EnvironmentResolverTest.php
@@ -88,6 +88,7 @@ public function testEnvironmentMap(string $envName, string $expected) : void {
    */
   public function environmentMapData() : array {
     return [
+      ['ci', 'test'],
       ['testing', 'test'],
       ['production', 'prod'],
       ['staging', 'stage'],