diff --git a/contacts.libraries.yml b/contacts.libraries.yml
index 8f444a1..207e2d4 100644
--- a/contacts.libraries.yml
+++ b/contacts.libraries.yml
@@ -74,3 +74,9 @@ contact:
   css:
     theme:
       css/contact.css: {}
+
+# Styling for the dedup page
+contacts_dedup_form:
+  css:
+    theme:
+      css/contacts.dedup.css: {}
diff --git a/contacts.routing.yml b/contacts.routing.yml
index 7bac45f..0cddcd3 100644
--- a/contacts.routing.yml
+++ b/contacts.routing.yml
@@ -119,3 +119,12 @@ contacts.manage.off_canvas_add:
         type: entity:contact_tab
   requirements:
     _permission: 'manage contacts dashboard'
+
+contacts.dedup:
+  path: '/admin/contacts/dedup'
+  defaults:
+    _form: '\Drupal\contacts\Form\DedupForm'
+  requirements:
+    _permission: 'manage contacts dashboard'
+  options:
+    theme: '' # Do not automatically apply the contacts theme (see DashboardNegotiator)
diff --git a/css/contacts.dedup.css b/css/contacts.dedup.css
new file mode 100644
index 0000000..2859148
--- /dev/null
+++ b/css/contacts.dedup.css
@@ -0,0 +1,11 @@
+.contact-dedupe-match {
+  color: green;
+}
+
+.contact-dedupe-conflict {
+  color: red;
+}
+
+.contact-dedupe-link {
+  float: right;
+}
diff --git a/src/Event/GetPropertiesToShowOnDedupScreenEvent.php b/src/Event/GetPropertiesToShowOnDedupScreenEvent.php
new file mode 100644
index 0000000..f18612f
--- /dev/null
+++ b/src/Event/GetPropertiesToShowOnDedupScreenEvent.php
@@ -0,0 +1,111 @@
+<?php
+
+namespace Drupal\contacts\Event;
+
+use Drupal\Component\Utility\SortArray;
+use Drupal\Core\Render\Element;
+use Symfony\Component\EventDispatcher\Event;
+
+/**
+ * Event raised to retrieve list of properties shown during merging.
+ *
+ * This event can be dispatched to retreive the properties that should be
+ * shown on the deduplication page.
+ *
+ * @package Drupal\contacts\Event
+ */
+class GetPropertiesToShowOnDedupScreenEvent extends Event {
+  const EVENT_NAME = 'contacts.dedup_property_info';
+
+
+  public $properties;
+
+  /**
+   * GetPropertiesToShowOnDedupScreenEvent constructor.
+   */
+  public function __construct() {
+    $this->properties = [
+      NULL => [
+        '#weight' => -99,
+        'mail' => [
+          'render field' => TRUE,
+          'compare' => TRUE,
+        ],
+        'profile_crm_indiv:entity:crm_gender' => [
+          'render field' => TRUE,
+          'compare' => TRUE,
+        ],
+      ],
+    ];
+  }
+
+  /**
+   * Get a list of properties to show on the dedup verification page.
+   *
+   * @return array
+   *   An array of properties to show in the comparison. Outer keys are group
+   *   labels (NULL is no group). Keys are property strings (a chain of metadata
+   *   wrapper properties separated by :). Values are arrays containing:
+   *   - label: Optional string to override the normal label.
+   *   - use label: Optionally attempt to use the EntityValueWrapper::label().
+   *   - render field: If the property is a field, setting this to TRUE will
+   *     render the property via the Field API.
+   *   - compare: A boolean indicating whether to run a comparison or a callable
+   *     for a custom comparison function (anonymous function recommended)
+   *   - strip html: TRUE if HTML should be stripped from the basic comparison.
+   *     Defaults to TRUE.
+   */
+  public function getPropertiesByWeight() {
+    // Sort everything by weight.
+    $weight = 0;
+    $info = &$this->properties;
+
+    foreach ($this->properties as &$properties) {
+      // Set a default weight on the group.
+      $properties += ['#weight' => $weight++ / 100];
+
+      // Set up our defaults on the properties.
+      foreach (Element::children($properties) as $property) {
+        $properties[$property] += [
+          '#weight' => $weight++ / 100,
+          'use label' => FALSE,
+          'render field' => FALSE,
+          'compare' => TRUE,
+          'strip html' => TRUE,
+        ];
+      }
+
+      // Sort the propreties.
+      uasort($properties, [SortArray::class, 'sortByWeightProperty']);
+
+      // Remove the weight.
+      foreach (Element::children($properties) as $property) {
+        unset($properties[$property]['#weight']);
+      }
+    }
+
+    // Sort the group.
+    uasort($info, [SortArray::class, 'sortByWeightProperty']);
+
+    // Remove group weights.
+    foreach ($info as &$properties) {
+      unset($properties['#weight']);
+    }
+
+    return $info;
+
+  }
+
+  /**
+   * Dispatches the event.
+   *
+   * @return static
+   */
+  public static function dispatch() {
+    $dispatcher = \Drupal::service('event_dispatcher');
+    $event = new static();
+    $dispatcher->dispatch(GetPropertiesToShowOnDedupScreenEvent::EVENT_NAME, $event);
+    return $event;
+  }
+
+}
diff --git a/src/Form/DedupForm.php b/src/Form/DedupForm.php
new file mode 100644
index 0000000..fb9aff1
--- /dev/null
+++ b/src/Form/DedupForm.php
@@ -0,0 +1,448 @@
+<?php
+
+namespace Drupal\contacts\Form;
+
+use Drupal\contacts\Event\GetPropertiesToShowOnDedupScreenEvent;
+use Drupal\Core\Datetime\DateFormatterInterface;
+use Drupal\Core\Form\FormBase;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Messenger\MessengerInterface;
+use Drupal\Core\Render\RendererInterface;
+use Drupal\entity_merge\Merger;
+use Drupal\field\Entity\FieldConfig;
+use Drupal\user\Entity\User;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Deduplicating/merging form.
+ */
+class DedupForm extends FormBase {
+
+  protected $renderer;
+  protected $messenger;
+  protected $dateFormatter;
+  protected $merger;
+
+  /**
+   * DedupForm constructor.
+   */
+  public function __construct(RendererInterface $renderer, MessengerInterface $messenger, DateFormatterInterface $date_formatter, Merger $merger) {
+    $this->renderer = $renderer;
+    $this->messenger = $messenger;
+    $this->dateFormatter = $date_formatter;
+    $this->merger = $merger;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('renderer'),
+      $container->get('messenger'),
+      $container->get('date.formatter'),
+      $container->get('entity_merge.merger')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return "contacts_dedup_form";
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state, $primary_contact_id = NULL, $secondary_contact_id = NULL) {
+    if (!$primary_contact_id || !$secondary_contact_id) {
+      $this->buildSelectionForm($form, $form_state);
+
+      // Contact IDs may have been supplied by the previous form submission.
+      $primary_contact_id = !empty($form_state->getValue('selection')['primary_party']) ? $form_state->getValue('selection')['primary_party'] : NULL;
+      $secondary_contact_id = !empty($form_state->getValue('selection')['secondary_party']) ? $form_state->getValue('selection')['secondary_party'] : NULL;
+    }
+
+    // Add our current selection (URL or form) for our merge submission.
+    $form['primary_party'] = [
+      '#type' => 'value',
+      '#value' => $primary_contact_id,
+    ];
+    $form['secondary_party'] = [
+      '#type' => 'value',
+      '#value' => $secondary_contact_id,
+    ];
+
+    // If we don't have both values, there is nothing more to do.
+    // Just render the selection form.
+    if (!$primary_contact_id || !$secondary_contact_id) {
+      return $form;
+    }
+
+    // If we're able to load our parties,
+    // show a verification table with details.
+    $this->buildMergeForm($form, $form_state, $primary_contact_id, $secondary_contact_id);
+
+    return $form;
+  }
+
+  /**
+   * Gets the values of the specified field form both primary and secondary.
+   *
+   * @param \Drupal\user\Entity\User $primary_contact
+   *   Primary contact for merge.
+   * @param \Drupal\user\Entity\User $secondary_contact
+   *   Secondary contact for merge.
+   * @param string $property
+   *   Name of property to render.
+   * @param array $info
+   *   Associative array with metadata about the property.
+   *
+   * @return array
+   *   Array containing 2 values (from primary and secondary contact).
+   *
+   * @throws \Exception
+   */
+  private function getFieldValuesToRender(User $primary_contact, User $secondary_contact, $property, array &$info) {
+    // Get our final value.
+    $v1_value = $v2_value = NULL;
+
+    $parts = explode(':', $property);
+    $final_part = array_pop($parts);
+
+    $v1 = $primary_contact;
+    $v2 = $secondary_contact;
+
+    foreach ($parts as $part) {
+      $v1 = $v1 && isset($v1->{$part}) ? $v1->{$part} : NULL;
+      $v2 = $v2 && isset($v2->{$part}) ? $v2->{$part} : NULL;
+
+      if ($v1 == NULL && $v2 == NULL) {
+        return [];
+      }
+    }
+
+    $property_info = $v1->get($final_part)->getFieldDefinition();
+
+    // If not set, pull through the label.
+    if (!isset($info['label'])) {
+      $info['label'] = $property_info->getLabel();
+    }
+
+    $fieldConfig = FieldConfig::loadByName($v1->getEntityTypeId(), $v1->bundle(), $final_part);
+
+    if ($fieldConfig != NULL && $info['render field']) {
+      $displayOptions = $fieldConfig->getDisplayOptions('default');
+      $displayOptions['label'] = 'hidden';
+
+      if ($v1->{$final_part}->value !== NULL) {
+        $v1_value = $v1->{$final_part}->view($displayOptions);
+        $v1_value = $this->renderer->render($v1_value);
+      }
+      if ($v2->{$final_part}->value !== NULL) {
+        $v2_value = $v2->{$final_part}->view($displayOptions);
+        $v2_value = $this->renderer->render($v2_value);
+      }
+    }
+    else {
+      // TODO: label/value switch not implemented yet.
+      // @codingStandardsIgnoreStart
+      // $method = $info['use label'] ? 'label' : 'value';
+      // $v1_value = $v1->hasField($final_part) && isset($v1->{$final_part}) ? $v1->{$final_part}->{$method}() : NULL;
+      // $v2_value = $v2 && $v2->value() && isset($v2->{$final_part}) ? $v2->{$final_part}->{$method}() : NULL;
+      // @codingStandardsIgnoreEnd
+      $v1_value = $v1->hasField($final_part) && isset($v1->{$final_part}) ? $v1->{$final_part}->value : NULL;
+      $v2_value = $v2->hasField($final_part) && isset($v2->{$final_part}) ? $v2->{$final_part}->value : NULL;
+
+      if (!$info['use label']) {
+        // If we don't have a list,
+        // wrap it in an array so we can process everything the same.
+        $type = $property_info->getType();
+        if (substr($type, 0, 5) != 'list<') {
+          $v1_value = isset($v1_value) ? [$v1_value] : NULL;
+          $v2_value = isset($v2_value) ? [$v2_value] : NULL;
+        }
+        else {
+          $type = $this->extractListType($type);
+        }
+
+        // Now loop over and do any processing on the type.
+        foreach (['v1_value', 'v2_value'] as $value) {
+          if (is_array($$value)) {
+            foreach ($$value as &$item) {
+              switch ($type) {
+                case 'date':
+                  $item = $this->dateFormatter->format($item);
+                  break;
+              }
+            }
+          }
+        }
+
+        // And convert back into a string.
+        $v1_value = is_array($v1_value) ? implode(', ', $v1_value) : $v1_value;
+        $v2_value = is_array($v2_value) ? implode(', ', $v2_value) : $v2_value;
+      }
+    }
+
+    return [$v1_value, $v2_value];
+  }
+
+  /**
+   * Builds the merge selection form.
+   */
+  private function buildSelectionForm(array &$form, FormStateInterface $form_state) {
+
+    // Show the selection form.
+    $form['selection'] = [
+      '#type' => 'fieldset',
+      '#title' => t('Select contacts to merge'),
+      '#description' => t('Enter the IDs of the contacts you want to merge.'),
+      '#tree' => TRUE,
+    ];
+    $form['selection']['#collapsible'] =
+    $form['selection']['#collapsed'] = $form_state->isSubmitted();
+
+    $form['selection']['primary_party'] = [
+      '#type' => 'textfield',
+      '#title' => t('Primary Contact Id'),
+      '#description' => t('Data from the secondary contact will be merged into this contact.'),
+      '#required' => TRUE,
+    ];
+
+    $form['selection']['secondary_party'] = [
+      '#type' => 'textfield',
+      '#title' => t('Duplicate contact id'),
+      '#description' => t('Data from this contact will be merged into the primary contact.'),
+      '#required' => TRUE,
+    ];
+
+    $form['selection']['actions'] = ['#type' => 'actions'];
+    $form['selection']['actions']['verify'] = [
+      '#type' => 'submit',
+      '#name' => 'verify_merge',
+      '#value' => t('Verify merge'),
+    ];
+
+  }
+
+  /**
+   * Builds the merge summary.
+   *
+   * @throws \Exception
+   */
+  private function buildMergeForm(array &$form, FormStateInterface $form_state, $primary_contact_id, $secondary_contact_id) {
+    /* @var $primary_contact \Drupal\user\Entity\User */
+    $primary_contact = User::load($primary_contact_id);
+    /* @var $secondary_contact \Drupal\user\Entity\User */
+    $secondary_contact = User::load($secondary_contact_id);
+
+    if ($primary_contact && $secondary_contact) {
+      $form['#attached']['library'][] = 'contacts/contacts_dedup_form';
+
+      $form['merge'] = [
+        '#type' => 'container',
+      ];
+      if (isset($form['selection'])) {
+        $form['merge']['#states'] = [
+          'visible' => [
+            ':input[name="selection[primary_party]"]' => ['value' => $primary_contact->id()],
+            ':input[name="selection[secondary_party]"]' => ['value' => $secondary_contact->id()],
+          ],
+        ];
+      }
+
+      $form['merge']['verify'] = [
+        '#theme' => 'table',
+        '#header' => [
+          ['header' => FALSE],
+          t('<strong>Primary</strong><br/>@label <small>[@pid]</small>', [
+            '@label' => $primary_contact->label(),
+            '@pid' => $primary_contact->id(),
+          ]),
+          t('<strong>Duplicate</strong><br/>@label <small>[@pid]</small>', [
+            '@label' => $secondary_contact->label(),
+            '@pid' => $secondary_contact->id(),
+          ]),
+        ],
+        '#rows' => [],
+      ];
+
+      $form['merge']['config'] = [];
+
+      // Capture a flag so that custom callbacks can prevent merges.
+      $prevent_merge = FALSE;
+
+      $property_groups = GetPropertiesToShowOnDedupScreenEvent::dispatch()
+        ->getPropertiesByWeight();
+
+      foreach ($property_groups as $group => $properties) {
+        if ($group) {
+          $group_header = [
+            [
+              'colspan' => 3,
+              'header' => TRUE,
+              'data' => $group,
+            ],
+          ];
+        }
+
+        foreach ($properties as $property => $info) {
+          list($v1_value, $v2_value) = $this->getFieldValuesToRender($primary_contact, $secondary_contact, $property, $info);
+
+          // If we don't have either value we can skip out.
+          if ($v1_value === NULL && $v2_value === NULL) {
+            continue;
+          }
+
+          // Output the group header if we have one.
+          if (isset($group_header)) {
+            $form['merge']['verify']['#rows'][$group] = $group_header;
+            unset($group_header);
+          }
+
+          // Build our row.
+          $row = [];
+          $row['data'][0] = $info['label'];
+          $row['data'][1] = $v1_value;
+          $row['data'][2]['data'] = $v2_value;
+
+          // Run the comparison if requested.
+          if ($info['compare']) {
+            $match = NULL;
+
+            // If a callable, pass onto the custom comparison.
+            if (is_callable($info['compare'])) {
+              $prevent_this_merge = FALSE;
+              $match = $info['compare']($v1_value, $v2_value, $prevent_this_merge, $form['merge']['config']);
+              $prevent_merge = $prevent_merge || $prevent_this_merge;
+            }
+            // Otherwise perform a simple string comparison.
+            elseif ($v1_value !== NULL && $v2_value !== NULL) {
+              if ($info['strip html']) {
+                $v1_value = isset($v1_value) ? strip_tags($v1_value) : $v1_value;
+                $v2_value = isset($v2_value) ? strip_tags($v2_value) : $v2_value;
+              }
+              $match = $v1_value == $v2_value;
+            }
+            elseif ($v1_value === NULL && $v2_value) {
+              $match = TRUE;
+            }
+
+            if (isset($match)) {
+              $row['data'][2]['class'][] = 'contact-dedupe-' . ($match ? 'match' : 'conflict');
+            }
+          }
+
+          // Add our row to the table.
+          $form['merge']['verify']['#rows'][$property] = $row;
+        }
+      }
+
+      $form['merge']['warning'] = [
+        '#type' => 'html_tag',
+        '#tag' => 'div',
+        '#attributes' => ['class' => ['messages', 'warning']],
+        '#value' => t('The colour coding provides an indication of what is likely to happen during the merge process. Results may vary according to specific circumstances.'),
+      ];
+
+      if ($prevent_merge) {
+        $form['merge']['prevented'] = [
+          '#type' => 'html_tag',
+          '#tag' => 'div',
+          '#attributes' => ['class' => ['messages', 'error']],
+          '#value' => t('This merge has been prevented. Please check for any at the top of the page.'),
+        ];
+      }
+
+      if (!empty($form['merge']['config'])) {
+        $form['merge']['config']['#type'] = 'fieldset';
+        $form['merge']['config']['#title'] = t('Additional settings');
+        $form['merge']['config']['#tree'] = TRUE;
+      }
+
+      $form['merge']['actions'] = [
+        '#type' => 'actions',
+        '#weight' => 100,
+        '#access' => !$prevent_merge,
+      ];
+
+      $form['merge']['actions']['submit'] = [
+        '#type' => 'submit',
+        '#name' => 'run_merge',
+        '#value' => t('Run merge'),
+      ];
+
+      // TODO Batch process not yet implemented.
+      // @codingStandardsIgnoreStart
+      /*// If we want to process immediately, add our batch submission handler.
+      if (variable_get('opencrm_dedupe_batch', 1)) {
+        $form['merge']['actions']['submit']['#submit'][] = 'opencrm_dedupe_party_merge_form_batch';
+      }*/
+      // @codingStandardsIgnoreEnd
+    }
+
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validateForm(array &$form, FormStateInterface $form_state) {
+    // When running a merge, make sure the user hasn't entered new IDs.
+    if ($form_state->getTriggeringElement()["#name"] == 'run_merge') {
+      // If we have the selection values, make sure they haven't been changed.
+      $primary_id_entered = $form_state->getValue('selection')['primary_party'];
+      $secondary_id_entered = $form_state->getValue('selection')['secondary_party'];
+
+      $primary_id_verified = $form_state->getValue('primary_party');
+      $secondary_id_verified = $form_state->getValue('secondary_party');
+
+      if (!empty($primary_id_entered) && !empty($primary_id_verified)) {
+        if ($primary_id_entered != $primary_id_verified) {
+          $form_state->setErrorByName('selection][primary_party', t('Please verify your new selection.'));
+        }
+      }
+
+      if (!empty($secondary_id_entered) && !empty($secondary_id_verified)) {
+        if ($secondary_id_entered != $secondary_id_verified) {
+          $form_state->setErrorByName('selection][secondary_party', t('Please verify your new selection.'));
+        }
+      }
+    }
+
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    if ($form_state->getTriggeringElement()['#name'] == 'run_merge') {
+      $primary_contact_id = $form_state->getValue("primary_party");
+      $secondary_contact_id = $form_state->getValue("secondary_party");
+      \Drupal::messenger()->addStatus("Running merge for $primary_contact_id and $secondary_contact_id");
+
+
+      $primary = User::load($primary_contact_id);
+      $secondary = User::load($secondary_contact_id);
+
+      $this->merger->merge($primary,$secondary);
+
+      $form_state->setRebuild();
+    }
+    else {
+      $form_state->setRebuild();
+    }
+  }
+
+  /**
+   * Extracts the underlying type from a list type.
+   */
+  private function extractListType($type) {
+    if (strpos($type, 'list<') === 0 && $type[strlen($type) - 1] == '>') {
+      return substr($type, 5, -1);
+    }
+    return FALSE;
+  }
+
+}
diff --git a/src/Theme/DashboardNegotiator.php b/src/Theme/DashboardNegotiator.php
index 2294ade..6828a28 100644
--- a/src/Theme/DashboardNegotiator.php
+++ b/src/Theme/DashboardNegotiator.php
@@ -28,6 +28,14 @@ public function applies(RouteMatchInterface $route_match) {
    */
   public function determineActiveTheme(RouteMatchInterface $route_match) {
     // Here you return the actual theme name.
+    // If the route provides a custom theme name, use it.
+    // Otherwise default to the contacts theme.
+    $route = $route_match->getRouteObject();
+
+    if ($route->hasOption('theme')) {
+      return $route->getOption('theme');
+    }
+
     return 'contacts_theme';
   }