diff --git a/ipynbsrv/core/models.py b/ipynbsrv/core/models.py
index 7d48146..bd959b3 100644
--- a/ipynbsrv/core/models.py
+++ b/ipynbsrv/core/models.py
@@ -772,7 +772,15 @@ class ContainerImage(models.Model):
         max_length=255,
         help_text='The primary key the backend uses to identify this image.'
     )
-    name = models.CharField(max_length=75)
+    name = models.CharField(
+        max_length=75,
+        validators=[
+            RegexValidator(
+                regex='^[A-z][\w\/]*$',
+                message='Invalid container snapshot name.'
+            )
+        ]
+    )
     description = models.TextField(blank=True, null=True)
     # TODO: document placeholders
     command = models.CharField(
diff --git a/ipynbsrv/web/templates/web/container_snapshots/modal_create.html b/ipynbsrv/web/templates/web/container_snapshots/modal_create.html
index d4ada7c..b87aa5e 100644
--- a/ipynbsrv/web/templates/web/container_snapshots/modal_create.html
+++ b/ipynbsrv/web/templates/web/container_snapshots/modal_create.html
@@ -14,6 +14,7 @@ <h4 class="modal-title">New Container Snapshot</h4>
                     <div class="form-group">
                         <label for="name">Name</label>
                         <input name="name" type="text" pattern="[A-Za-z1-9_-]+" class="form-control" required>
+                        <p class="help-text">Allowed pattern: ^[A-z]\w*$</p>
                     </div>
                     <div class="form-group">
                         <label for="description">Description</label>
diff --git a/ipynbsrv/web/templates/web/images/modal_create.html b/ipynbsrv/web/templates/web/images/modal_create.html
index 57417a8..865e5d3 100644
--- a/ipynbsrv/web/templates/web/images/modal_create.html
+++ b/ipynbsrv/web/templates/web/images/modal_create.html
@@ -22,6 +22,7 @@ <h4 class="modal-title">New image</h4>
                     <div class="form-group">
                         <label for="img_name">Name</label>
                         <input name="img_name" type="text" pattern="[A-Za-z1-9_-]+" class="form-control" placeholder="e.g fhnw-maths " required>
+                        <p class="help-text">Allowed pattern: ^[A-z][\w\/]*$</p>
                     </div>
                     <div class="form-group">
                         <label for="description">Description</label>
diff --git a/ipynbsrv/web/templates/web/shares/modal_create.html b/ipynbsrv/web/templates/web/shares/modal_create.html
index f00134f..c4bb05b 100644
--- a/ipynbsrv/web/templates/web/shares/modal_create.html
+++ b/ipynbsrv/web/templates/web/shares/modal_create.html
@@ -12,7 +12,8 @@ <h4 class="modal-title">New shared folder</h4>
                 <div class="modal-body">
                     <div class="form-group">
                         <label for="name">Name</label>
-                        <input type="text" pattern="[A-Za-z1-9_-]+" class="form-control" name="name" placeholder="maths" required>
+                        <input type="text" pattern="^[A-z]\w*$" class="form-control" name="name" placeholder="maths" required>
+                        <p class="help-block">Allowed pattern: ^[A-z]\w*$</p>
                     </div>
                     <div class="form-group">
                         <label for="description">Description</label>