diff --git a/fn/ht.php b/fn/ht.php
index 1a2ea21..bc2d388 100644
--- a/fn/ht.php
+++ b/fn/ht.php
@@ -1,5 +1,7 @@
 <?php
 
+const SUBPATH_REGEX = '^[a-z0-9-]{4,63}$';
+
 function htSetupUserFs($id) {
 	// Setup SFTP directory
 	if (mkdir(CONF['ht']['ht_path'] . '/fs/' . $id, 0000) !== true)
diff --git a/fn/reg.php b/fn/reg.php
index 91c8b8d..fa1c4aa 100644
--- a/fn/reg.php
+++ b/fn/reg.php
@@ -1,6 +1,6 @@
 <?php
 
-const SUBDOMAIN_REGEX = '^[a-z0-9]{4,63}$';
+const SUBDOMAIN_REGEX = '^(?!\-)(?!..\-\-)[a-z0-9-]{4,63}(?<!\-)$';
 
 function regListUserDomains() {
 	if (isset($_SESSION['id']))
diff --git a/locales/fr/C/LC_MESSAGES/messages.po b/locales/fr/C/LC_MESSAGES/messages.po
index 88c8271..7a2e1d0 100644
--- a/locales/fr/C/LC_MESSAGES/messages.po
+++ b/locales/fr/C/LC_MESSAGES/messages.po
@@ -1,7 +1,7 @@
 msgid ""
 msgstr ""
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2023-06-02 22:42+0200\n"
+"POT-Creation-Date: 2023-06-04 23:57+0200\n"
 "Language: fr\n"
 "Content-Type: text/plain; charset=UTF-8\n"
 
@@ -274,15 +274,15 @@ msgstr "Supprimer un accès"
 msgid "Delete an existing HTTP access from a subdirectory of the SFTP space"
 msgstr "Retirer un accès HTTP existant d'un sous-dossier de l'espace SFTP"
 
-#: router.php:151 view.php:39
+#: router.php:152 view.php:39
 msgid "This service is currently under maintenance. No action can be taken on it until an administrator finishes repairing it."
 msgstr "Ce service est en cours de maintenance. Aucune action ne peut être effectuée avant qu'ane administrataire termine de le réparer."
 
-#: router.php:161
+#: router.php:162
 msgid "You need to be logged in to do this."
 msgstr "Vous devez être connecté·e à un compte pour faire cela."
 
-#: router.php:163
+#: router.php:164
 msgid "This account doesn't exist anymore. Log out to end this ghost session."
 msgstr "Ce compte n'existe plus. Déconnectez-vous pour terminer cette session fantôme."
 
@@ -336,7 +336,7 @@ msgstr "Preuve incorrecte."
 msgid "IP address malformed."
 msgstr "Adresse IP malformée."
 
-#: fn/dns.php:68 fn/ht.php:28
+#: fn/dns.php:68 fn/ht.php:30
 msgid "Domain malformed."
 msgstr "Domaine malformé."
 
@@ -672,28 +672,38 @@ msgstr "Le domaine doit avoir les enregistrements suivants pendant le traitement
 #: pg-view/ht/add-dns.php:29 pg-view/ns/form.ns.php:8 pg-view/ns/print.php:32
 #: pg-view/ns/zone-add.php:6 pg-view/reg/ds.php:8 pg-view/reg/glue.php:8
 #: pg-view/reg/glue.php:15 pg-view/reg/ns.php:8 pg-view/reg/print.php:2
-#: pg-view/reg/print.php:16 pg-view/reg/register.php:7
+#: pg-view/reg/print.php:16 pg-view/reg/register.php:11
 #: pg-view/reg/unregister.php:6
 msgid "Domain"
 msgstr "Domaine"
 
 #: pg-view/ht/add-dns.php:31 pg-view/ht/add-onion.php:2
-#: pg-view/ht/add-subdomain.php:4 pg-view/ht/add-subpath.php:4
+#: pg-view/ht/add-subdomain.php:8 pg-view/ht/add-subpath.php:8
 msgid "Target directory"
 msgstr "Dossier ciblé"
 
 #: pg-view/ht/add-dns.php:40 pg-view/ht/add-onion.php:11
-#: pg-view/ht/add-subdomain.php:13 pg-view/ht/add-subpath.php:13
+#: pg-view/ht/add-subdomain.php:17 pg-view/ht/add-subpath.php:17
 msgid "Setup access"
 msgstr "Créer l'accès"
 
-#: pg-view/ht/add-subdomain.php:2 pg-view/ns/form.ns.php:10
-#: pg-view/reg/glue.php:10 pg-view/reg/register.php:9
+#: pg-view/ht/add-subdomain.php:2 pg-view/reg/register.php:6
+#, php-format
+msgid "The subdomain can only contain %1$s, %2$s and %3$s, and must be between 4 and 63 characters. It can't have an hyphen (%3$s) in first, last or both third and fourth position."
+msgstr "Le sous-domain peut uniquement contenir %1$s, %2$s et %3$s, et doit être entre 4 et 63 caractères. Il ne peut pas avoir un tiret (%3$s) en première, dernière ou à la fois troisième et quatrième position."
+
+#: pg-view/ht/add-subdomain.php:6 pg-view/ns/form.ns.php:10
+#: pg-view/reg/glue.php:10 pg-view/reg/register.php:13
 #: pg-view/reg/transfer.php:9
 msgid "Subdomain"
 msgstr "Sous-domaine"
 
 #: pg-view/ht/add-subpath.php:2
+#, php-format
+msgid "The path can only contain %1$s, %2$s and %3$s, and must be between 4 and 63 characters."
+msgstr "Le chemin peut uniquement contenir %1$s, %2$s et %3$s, et doit être entre 4 et 63 caractères."
+
+#: pg-view/ht/add-subpath.php:6
 msgid "Path"
 msgstr "Chemin"
 
@@ -1126,18 +1136,18 @@ msgid "Nobody can register a domain under these suffixes:"
 msgstr "Personne ne peut enregistrer un domain sous ces suffixes&nbsp;:"
 
 #: pg-view/reg/register.php:2
-msgid "Register a new domain on your account. It must consist of between 4 and 63 letters and digits."
-msgstr "Enregistrer un nouveau domaine sur son compte. Il doit être composé d'entre 4 et 63 lettres et chiffres."
+msgid "Register a new domain on your account."
+msgstr "Enregistrer un nouveau domaine sur son compte."
 
-#: pg-view/reg/register.php:14 pg-view/reg/transfer.php:14
+#: pg-view/reg/register.php:18 pg-view/reg/transfer.php:14
 msgid "Suffix"
 msgstr "Suffixe"
 
-#: pg-view/reg/register.php:27
+#: pg-view/reg/register.php:31
 msgid "Check availability"
 msgstr "Vérifier sa disponibilité"
 
-#: pg-view/reg/register.php:29
+#: pg-view/reg/register.php:33
 msgid "Register"
 msgstr "Enregistrer"
 
diff --git a/locales/messages.pot b/locales/messages.pot
index 0510563..1e7bd9c 100644
--- a/locales/messages.pot
+++ b/locales/messages.pot
@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PACKAGE VERSION\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2023-06-02 22:42+0200\n"
+"POT-Creation-Date: 2023-06-04 23:57+0200\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -286,15 +286,15 @@ msgstr ""
 msgid "Delete an existing HTTP access from a subdirectory of the SFTP space"
 msgstr ""
 
-#: router.php:151 view.php:39
+#: router.php:152 view.php:39
 msgid "This service is currently under maintenance. No action can be taken on it until an administrator finishes repairing it."
 msgstr ""
 
-#: router.php:161
+#: router.php:162
 msgid "You need to be logged in to do this."
 msgstr ""
 
-#: router.php:163
+#: router.php:164
 msgid "This account doesn't exist anymore. Log out to end this ghost session."
 msgstr ""
 
@@ -348,7 +348,7 @@ msgstr ""
 msgid "IP address malformed."
 msgstr ""
 
-#: fn/dns.php:68 fn/ht.php:28
+#: fn/dns.php:68 fn/ht.php:30
 msgid "Domain malformed."
 msgstr ""
 
@@ -684,28 +684,38 @@ msgstr ""
 #: pg-view/ht/add-dns.php:29 pg-view/ns/form.ns.php:8 pg-view/ns/print.php:32
 #: pg-view/ns/zone-add.php:6 pg-view/reg/ds.php:8 pg-view/reg/glue.php:8
 #: pg-view/reg/glue.php:15 pg-view/reg/ns.php:8 pg-view/reg/print.php:2
-#: pg-view/reg/print.php:16 pg-view/reg/register.php:7
+#: pg-view/reg/print.php:16 pg-view/reg/register.php:11
 #: pg-view/reg/unregister.php:6
 msgid "Domain"
 msgstr ""
 
 #: pg-view/ht/add-dns.php:31 pg-view/ht/add-onion.php:2
-#: pg-view/ht/add-subdomain.php:4 pg-view/ht/add-subpath.php:4
+#: pg-view/ht/add-subdomain.php:8 pg-view/ht/add-subpath.php:8
 msgid "Target directory"
 msgstr ""
 
 #: pg-view/ht/add-dns.php:40 pg-view/ht/add-onion.php:11
-#: pg-view/ht/add-subdomain.php:13 pg-view/ht/add-subpath.php:13
+#: pg-view/ht/add-subdomain.php:17 pg-view/ht/add-subpath.php:17
 msgid "Setup access"
 msgstr ""
 
-#: pg-view/ht/add-subdomain.php:2 pg-view/ns/form.ns.php:10
-#: pg-view/reg/glue.php:10 pg-view/reg/register.php:9
+#: pg-view/ht/add-subdomain.php:2 pg-view/reg/register.php:6
+#, php-format
+msgid "The subdomain can only contain %1$s, %2$s and %3$s, and must be between 4 and 63 characters. It can't have an hyphen (%3$s) in first, last or both third and fourth position."
+msgstr ""
+
+#: pg-view/ht/add-subdomain.php:6 pg-view/ns/form.ns.php:10
+#: pg-view/reg/glue.php:10 pg-view/reg/register.php:13
 #: pg-view/reg/transfer.php:9
 msgid "Subdomain"
 msgstr ""
 
 #: pg-view/ht/add-subpath.php:2
+#, php-format
+msgid "The path can only contain %1$s, %2$s and %3$s, and must be between 4 and 63 characters."
+msgstr ""
+
+#: pg-view/ht/add-subpath.php:6
 msgid "Path"
 msgstr ""
 
@@ -1138,18 +1148,18 @@ msgid "Nobody can register a domain under these suffixes:"
 msgstr ""
 
 #: pg-view/reg/register.php:2
-msgid "Register a new domain on your account. It must consist of between 4 and 63 letters and digits."
+msgid "Register a new domain on your account."
 msgstr ""
 
-#: pg-view/reg/register.php:14 pg-view/reg/transfer.php:14
+#: pg-view/reg/register.php:18 pg-view/reg/transfer.php:14
 msgid "Suffix"
 msgstr ""
 
-#: pg-view/reg/register.php:27
+#: pg-view/reg/register.php:31
 msgid "Check availability"
 msgstr ""
 
-#: pg-view/reg/register.php:29
+#: pg-view/reg/register.php:33
 msgid "Register"
 msgstr ""
 
diff --git a/pg-act/ht/add-subdomain.php b/pg-act/ht/add-subdomain.php
index 8bd2c96..0a1b667 100644
--- a/pg-act/ht/add-subdomain.php
+++ b/pg-act/ht/add-subdomain.php
@@ -3,7 +3,7 @@
 if (dirsStatuses('subdomain')[$_POST['dir']] !== false)
 	output(403, 'Wrong value for <code>dir</code>.');
 
-if (preg_match('/^[a-z0-9]{1,32}$/D', $_POST['subdomain']) !== 1)
+if (preg_match('/' . SUBDOMAIN_REGEX . '/D', $_POST['subdomain']) !== 1)
 	output(403, _('Invalid domain label.'));
 
 if (query('select', 'sites', ['address' => $_POST['subdomain'], 'type' => 'subdomain']) !== [])
diff --git a/pg-act/ht/add-subpath.php b/pg-act/ht/add-subpath.php
index 8f83761..e0bb139 100644
--- a/pg-act/ht/add-subpath.php
+++ b/pg-act/ht/add-subpath.php
@@ -3,7 +3,7 @@
 if (dirsStatuses('subpath')[$_POST['dir']] !== false)
 	output(403, 'Wrong value for <code>dir</code>.');
 
-if (preg_match('/^[a-z0-9]{1,32}$/D', $_POST['path']) !== 1)
+if (preg_match('/' . SUBPATH_REGEX . '/D', $_POST['path']) !== 1)
 	output(403, _('Invalid path.'));
 
 if (query('select', 'sites', ['address' => $_POST['path'], 'type' => 'subpath']) !== [])
diff --git a/pg-view/ht/add-subdomain.php b/pg-view/ht/add-subdomain.php
index b0d8125..3fce989 100644
--- a/pg-view/ht/add-subdomain.php
+++ b/pg-view/ht/add-subdomain.php
@@ -1,3 +1,7 @@
+<p>
+	<?= sprintf(_('The subdomain can only contain %1$s, %2$s and %3$s, and must be between 4 and 63 characters. It can\'t have an hyphen (%3$s) in first, last or both third and fourth position.'), '<abbr title="abcdefghijklmnopqrstuvwxyz"><code>a</code>-<code>z</code></abbr>',  '<abbr title="0123456789"><code>0</code>-<code>9</code></abbr>', '<code>-</code>') ?>
+</p>
+
 <form method="post">
 	<label for="subdomain"><?= _('Subdomain') ?></label><br>
 	<input required="" placeholder="label" id="subdomain" name="subdomain" type="text"><code>.<?= CONF['ht']['subdomain_domain'] ?></code><br>
diff --git a/pg-view/ht/add-subpath.php b/pg-view/ht/add-subpath.php
index 784f6d1..948abc4 100644
--- a/pg-view/ht/add-subpath.php
+++ b/pg-view/ht/add-subpath.php
@@ -1,6 +1,10 @@
+<p>
+	<?= sprintf(_('The path can only contain %1$s, %2$s and %3$s, and must be between 4 and 63 characters.'), '<abbr title="abcdefghijklmnopqrstuvwxyz"><code>a</code>-<code>z</code></abbr>',  '<abbr title="0123456789"><code>0</code>-<code>9</code></abbr>', '<code>-</code>') ?>
+</p>
+
 <form method="post">
 	<label for="path"><?= _('Path') ?></label><br>
-	<code>https://<?= CONF['ht']['subpath_domain'] ?>/</code><input required="" placeholder="path" id="path" name="path" type="text"><br>
+	<code>https://<?= CONF['ht']['subpath_domain'] ?>/</code><input required="" pattern="<?= SUBPATH_REGEX ?>" placeholder="path" id="path" name="path" type="text"><br>
 	<label for="dir"><?= _('Target directory') ?></label><br>
 	<select required="" name="dir" id="dir">
 		<option value="" disabled="" selected="">—</option>
diff --git a/pg-view/reg/register.php b/pg-view/reg/register.php
index 74f2ce2..522257e 100644
--- a/pg-view/reg/register.php
+++ b/pg-view/reg/register.php
@@ -1,5 +1,9 @@
 <p>
-	<?= _('Register a new domain on your account. It must consist of between 4 and 63 letters and digits.') ?>
+	<?= _('Register a new domain on your account.') ?>
+</p>
+
+<p>
+	<?= sprintf(_('The subdomain can only contain %1$s, %2$s and %3$s, and must be between 4 and 63 characters. It can\'t have an hyphen (%3$s) in first, last or both third and fourth position.'), '<abbr title="abcdefghijklmnopqrstuvwxyz"><code>a</code>-<code>z</code></abbr>',  '<abbr title="0123456789"><code>0</code>-<code>9</code></abbr>', '<code>-</code>') ?>
 </p>
 
 <form method="post">