diff --git a/src/Form/Type/UiElement/ButtonLinkType.php b/src/Form/Type/UiElement/ButtonLinkType.php
index 8bd6d7e6..f8008387 100644
--- a/src/Form/Type/UiElement/ButtonLinkType.php
+++ b/src/Form/Type/UiElement/ButtonLinkType.php
@@ -32,12 +32,28 @@ public function buildForm(FormBuilderInterface $builder, array $options): void
                 new Assert\NotBlank([]),
             ];
             $constraintsLink = [
-                new Assert\Url([]),
+                new Assert\AtLeastOneOf([
+                    'includeInternalMessages' => false,
+                    'message' => 'monsieurbiz_richeditor_plugin.not_valid_url',
+                    'constraints' => [
+                        new Assert\Url(['protocols' => ['http', 'https'], 'relativeProtocol' => true]),
+                        new Assert\Regex(['pattern' => '`^(#|/[^/])`']),
+                    ],
+                ]),
                 new Assert\NotBlank([]),
             ];
         } else {
             $constraintsLabel = [];
-            $constraintsLink = [];
+            $constraintsLink = [
+                new Assert\AtLeastOneOf([
+                    'includeInternalMessages' => false,
+                    'message' => 'monsieurbiz_richeditor_plugin.not_valid_url',
+                    'constraints' => [
+                        new Assert\Url(['protocols' => ['http', 'https'], 'relativeProtocol' => true]),
+                        new Assert\Regex(['pattern' => '`^(#|/[^/])`']),
+                    ],
+                ]),
+            ];
         }
 
         $builder
diff --git a/src/Form/Type/UiElement/ImageType.php b/src/Form/Type/UiElement/ImageType.php
index c33ead69..89b0900c 100644
--- a/src/Form/Type/UiElement/ImageType.php
+++ b/src/Form/Type/UiElement/ImageType.php
@@ -29,6 +29,12 @@ class ImageType extends AbstractType
      * @inheritdoc
      */
     public function buildForm(FormBuilderInterface $builder, array $options): void
+    {
+        $this->addFields($builder, $options);
+        $this->addEvents($builder, $options);
+    }
+
+    public function addFields(FormBuilderInterface $builder, array $options): void
     {
         $builder
             ->add('image', FileType::class, [
@@ -49,12 +55,22 @@ public function buildForm(FormBuilderInterface $builder, array $options): void
                 'required' => false,
                 'label' => 'monsieurbiz_richeditor_plugin.ui_element.monsieurbiz.image.field.link',
                 'constraints' => [
-                    new Assert\Url([]),
+                    new Assert\AtLeastOneOf([
+                        'includeInternalMessages' => false,
+                        'message' => 'monsieurbiz_richeditor_plugin.not_valid_url',
+                        'constraints' => [
+                            new Assert\Url(['protocols' => ['http', 'https'], 'relativeProtocol' => true]),
+                            new Assert\Regex(['pattern' => '`^(#|/[^/])`']),
+                        ],
+                    ]),
                 ],
             ])
             ->add('align', AlignmentType::class)
         ;
+    }
 
+    public function addEvents(FormBuilderInterface $builder, array $options): void
+    {
         $builder->addEventListener(FormEvents::PRE_SUBMIT, function (FormEvent $event): void {
             // Change image field constraints depending on submitted value
             $options = $event->getForm()->get('image')->getConfig()->getOptions();
diff --git a/src/Form/Type/UiElement/VideoType.php b/src/Form/Type/UiElement/VideoType.php
index ffc3fbad..3d2dda7f 100644
--- a/src/Form/Type/UiElement/VideoType.php
+++ b/src/Form/Type/UiElement/VideoType.php
@@ -27,6 +27,12 @@ class VideoType extends AbstractType
      * @inheritdoc
      */
     public function buildForm(FormBuilderInterface $builder, array $options): void
+    {
+        $this->addFields($builder, $options);
+        $this->addEvents($builder, $options);
+    }
+
+    public function addFields(FormBuilderInterface $builder, array $options): void
     {
         $builder
             ->add('video', FileType::class, [
@@ -43,7 +49,10 @@ public function buildForm(FormBuilderInterface $builder, array $options): void
             ])
             ->add('align', AlignmentType::class)
         ;
+    }
 
+    public function addEvents(FormBuilderInterface $builder, array $options): void
+    {
         $builder->addEventListener(FormEvents::PRE_SUBMIT, function (FormEvent $event): void {
             // Change video field constraints depending on submitted value
             $options = $event->getForm()->get('video')->getConfig()->getOptions();
diff --git a/src/Resources/translations/validators.en.yaml b/src/Resources/translations/validators.en.yaml
new file mode 100644
index 00000000..eb22719e
--- /dev/null
+++ b/src/Resources/translations/validators.en.yaml
@@ -0,0 +1,2 @@
+monsieurbiz_richeditor_plugin:
+    not_valid_url: 'This value is not a valid URL (absolute or relative) or a valid hashtag.'
diff --git a/src/Resources/translations/validators.fr.yaml b/src/Resources/translations/validators.fr.yaml
new file mode 100644
index 00000000..fd1fa81c
--- /dev/null
+++ b/src/Resources/translations/validators.fr.yaml
@@ -0,0 +1,2 @@
+monsieurbiz_richeditor_plugin:
+    not_valid_url: 'Cette valeur n''est pas une URL valide (absolue ou relative) ou un hashtag valide.'