diff --git a/resources/celerity/map.php b/resources/celerity/map.php
index 0190255a22..61887a64e1 100644
--- a/resources/celerity/map.php
+++ b/resources/celerity/map.php
@@ -146,6 +146,7 @@ return array(
     'rsrc/css/phui/phui-image-mask.css' => 'a8498f9c',
     'rsrc/css/phui/phui-info-panel.css' => '27ea50a1',
     'rsrc/css/phui/phui-info-view.css' => '28efab79',
+    'rsrc/css/phui/phui-invisible-character-view.css' => '6993d9f0',
     'rsrc/css/phui/phui-list.css' => '9da2aa00',
     'rsrc/css/phui/phui-object-box.css' => '6b487c57',
     'rsrc/css/phui/phui-object-item-list-view.css' => '87278fa0',
@@ -922,6 +923,7 @@ return array(
     'phui-info-panel-css' => '27ea50a1',
     'phui-info-view-css' => '28efab79',
     'phui-inline-comment-view-css' => '5953c28e',
+    'phui-invisible-character-view-css' => '6993d9f0',
     'phui-list-view-css' => '9da2aa00',
     'phui-object-box-css' => '6b487c57',
     'phui-object-item-list-view-css' => '87278fa0',
diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
index a38984339b..bbd0bbab2b 100644
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -1652,6 +1652,8 @@ phutil_register_library_map(array(
     'PHUIInfoPanelExample' => 'applications/uiexample/examples/PHUIInfoPanelExample.php',
     'PHUIInfoPanelView' => 'view/phui/PHUIInfoPanelView.php',
     'PHUIInfoView' => 'view/form/PHUIInfoView.php',
+    'PHUIInvisibleCharacterTestCase' => 'view/phui/__tests__/PHUIInvisibleCharacterTestCase.php',
+    'PHUIInvisibleCharacterView' => 'view/phui/PHUIInvisibleCharacterView.php',
     'PHUIListExample' => 'applications/uiexample/examples/PHUIListExample.php',
     'PHUIListItemView' => 'view/phui/PHUIListItemView.php',
     'PHUIListView' => 'view/phui/PHUIListView.php',
@@ -6320,6 +6322,8 @@ phutil_register_library_map(array(
     'PHUIInfoPanelExample' => 'PhabricatorUIExample',
     'PHUIInfoPanelView' => 'AphrontView',
     'PHUIInfoView' => 'AphrontView',
+    'PHUIInvisibleCharacterTestCase' => 'PhabricatorTestCase',
+    'PHUIInvisibleCharacterView' => 'AphrontView',
     'PHUIListExample' => 'PhabricatorUIExample',
     'PHUIListItemView' => 'AphrontTagView',
     'PHUIListView' => 'AphrontTagView',
diff --git a/src/applications/auth/controller/PhabricatorAuthRegisterController.php b/src/applications/auth/controller/PhabricatorAuthRegisterController.php
index 1d036b13a9..3e4135fff5 100644
--- a/src/applications/auth/controller/PhabricatorAuthRegisterController.php
+++ b/src/applications/auth/controller/PhabricatorAuthRegisterController.php
@@ -89,13 +89,14 @@ final class PhabricatorAuthRegisterController
       // user expectation and it's not clear the cases it enables are valuable.
       // See discussion in T3472.
       if (!PhabricatorUserEmail::isAllowedAddress($default_email)) {
+        $debug_email = new PHUIInvisibleCharacterView($default_email);
         return $this->renderError(
           array(
             pht(
               'The account you are attempting to register with has an invalid '.
               'email address (%s). This Phabricator install only allows '.
               'registration with specific email addresses:',
-              $default_email),
+              $debug_email),
             phutil_tag('br'),
             phutil_tag('br'),
             PhabricatorUserEmail::describeAllowedAddresses(),
diff --git a/src/applications/phurl/editor/PhabricatorPhurlURLEditor.php b/src/applications/phurl/editor/PhabricatorPhurlURLEditor.php
index 64cfe6046b..9fe55bcbeb 100644
--- a/src/applications/phurl/editor/PhabricatorPhurlURLEditor.php
+++ b/src/applications/phurl/editor/PhabricatorPhurlURLEditor.php
@@ -123,18 +123,23 @@ final class PhabricatorPhurlURLEditor
         foreach ($xactions as $xaction) {
           if ($xaction->getOldValue() != $xaction->getNewValue()) {
             $new_alias = $xaction->getNewValue();
+            $debug_alias = new PHUIInvisibleCharacterView($new_alias);
             if (!preg_match('/[a-zA-Z]/', $new_alias)) {
               $errors[] = new PhabricatorApplicationTransactionValidationError(
                 $type,
                 pht('Invalid Alias'),
-                pht('The alias must contain at least one letter.'),
+                pht('The alias you provided (%s) must contain at least one '.
+                  'letter.',
+                  $debug_alias),
                 $xaction);
             }
             if (preg_match('/[^a-z0-9]/i', $new_alias)) {
               $errors[] = new PhabricatorApplicationTransactionValidationError(
                 $type,
                 pht('Invalid Alias'),
-                pht('The alias may only contain letters and numbers.'),
+                pht('The alias you provided (%s) may only contain letters and '.
+                  'numbers.',
+                  $debug_alias),
                 $xaction);
             }
           }
diff --git a/src/view/phui/PHUIInvisibleCharacterView.php b/src/view/phui/PHUIInvisibleCharacterView.php
new file mode 100644
index 0000000000..dda00f81a1
--- /dev/null
+++ b/src/view/phui/PHUIInvisibleCharacterView.php
@@ -0,0 +1,94 @@
+<?php
+
+/**
+ * API for replacing whitespace characters and some control characters with
+ * their printable representations. This is useful for debugging and
+ * displaying more helpful error messages to users.
+ *
+ */
+final class PHUIInvisibleCharacterView extends AphrontView {
+
+  private $inputText;
+  private $plainText = false;
+
+  // This is a list of the common invisible characters that are
+  // actually typeable. Other invisible characters will simply
+  // be displayed as their hex representations.
+  private static $invisibleChars = array(
+    "\x00" => 'NULL',
+    "\t" => 'TAB',
+    "\n" => 'NEWLINE',
+    "\x20" => 'SPACE',
+    );
+
+  public function __construct($input_text) {
+    $this->inputText = $input_text;
+  }
+
+  public function setPlainText($plain_text) {
+    $this->plainText = $plain_text;
+    return $this;
+  }
+
+  public function getStringParts() {
+    $input_text = $this->inputText;
+    $text_array = phutil_utf8v($input_text);
+
+    for ($ii = 0; $ii < count($text_array); $ii++) {
+      $char = $text_array[$ii];
+      $char_hex = bin2hex($char);
+      if (array_key_exists($char, self::$invisibleChars)) {
+        $text_array[$ii] = array(
+          'special' => true,
+          'value' => '<'.self::$invisibleChars[$char].'>',
+          );
+      } else if (ord($char) < 32) {
+        $text_array[$ii] = array(
+          'special' => true,
+          'value' => '<0x'.$char_hex.'>',
+          );
+      } else {
+        $text_array[$ii] = array(
+          'special' => false,
+          'value' => $char,
+          );
+      }
+    }
+    return $text_array;
+  }
+
+  private function renderHtmlArray() {
+    $html_array = array();
+    $parts = $this->getStringParts();
+    foreach ($parts as $part) {
+      if ($part['special']) {
+        $html_array[] = phutil_tag(
+          'span',
+          array('class' => 'invisible-special'),
+          $part['value']);
+      } else {
+        $html_array[] = $part['value'];
+      }
+    }
+    return $html_array;
+  }
+
+  private function renderPlainText() {
+    $parts = $this->getStringParts();
+    $res = '';
+    foreach ($parts as $part) {
+      $res .= $part['value'];
+    }
+    return $res;
+  }
+
+  public function render() {
+    require_celerity_resource('phui-invisible-character-view-css');
+    if ($this->plainText) {
+      return $this->renderPlainText();
+    } else {
+      return $this->renderHtmlArray();
+    }
+  }
+
+}
diff --git a/src/view/phui/__tests__/PHUIInvisibleCharacterTestCase.php b/src/view/phui/__tests__/PHUIInvisibleCharacterTestCase.php
new file mode 100644
index 0000000000..09f8c0934b
--- /dev/null
+++ b/src/view/phui/__tests__/PHUIInvisibleCharacterTestCase.php
@@ -0,0 +1,52 @@
+<?php
+
+final class PHUIInvisibleCharacterTestCase extends PhabricatorTestCase {
+
+  public function testEmptyString() {
+    $view = new PHUIInvisibleCharacterView('');
+    $res = $view->render();
+    $this->assertEqual($res, array());
+  }
+
+  public function testEmptyPlainText() {
+    $view = (new PHUIInvisibleCharacterView(''))
+      ->setPlainText(true);
+    $res = $view->render();
+    $this->assertEqual($res, '');
+  }
+
+  public function testWithNamedChars() {
+    $test_input = "\x00\n\t ";
+    $view = (new PHUIInvisibleCharacterView($test_input))
+      ->setPlainText(true);
+    $res = $view->render();
+    $this->assertEqual($res, '<NULL><NEWLINE><TAB><SPACE>');
+  }
+
+  public function testWithHexChars() {
+    $test_input = "abc\x01";
+    $view = (new PHUIInvisibleCharacterView($test_input))
+      ->setPlainText(true);
+    $res = $view->render();
+    $this->assertEqual($res, 'abc<0x01>');
+  }
+
+  public function testWithNamedAsHex() {
+    $test_input = "\x00\x0a\x09\x20";
+    $view = (new PHUIInvisibleCharacterView($test_input))
+      ->setPlainText(true);
+    $res = $view->render();
+    $this->assertEqual($res, '<NULL><NEWLINE><TAB><SPACE>');
+  }
+
+  public function testHtmlDecoration() {
+    $test_input = "a\x00\n\t ";
+    $view = new PHUIInvisibleCharacterView($test_input);
+    $res = $view->render();
+    $this->assertFalse($res[0] instanceof PhutilSafeHTML);
+    $this->assertTrue($res[1] instanceof PhutilSafeHTML);
+    $this->assertTrue($res[2] instanceof PhutilSafeHTML);
+    $this->assertTrue($res[3] instanceof PhutilSafeHTML);
+    $this->assertTrue($res[4] instanceof PhutilSafeHTML);
+  }
+}
diff --git a/webroot/rsrc/css/phui/phui-invisible-character-view.css b/webroot/rsrc/css/phui/phui-invisible-character-view.css
new file mode 100644
index 0000000000..b8a848fa9a
--- /dev/null
+++ b/webroot/rsrc/css/phui/phui-invisible-character-view.css
@@ -0,0 +1,12 @@
+/**
+ * @provides phui-invisible-character-view-css
+ */
+
+.invisible-special {
+  font-family: monospace;
+  color: #000;
+  background: rgba({$alphablue},0.1);
+  padding: 1px 4px;
+  border-radius: 3px;
+  white-space: pre-wrap;
+}