diff --git a/js/battle.js b/js/battle.js
index aac7ef018..d0d8594d1 100644
--- a/js/battle.js
+++ b/js/battle.js
@@ -5154,7 +5154,7 @@ function Battle(frame, logFrame, noPreload) {
 		case 'debug':
 			args.shift();
 			name = args.join(' ');
-			self.log('<div class="chat"><small style="color:#999">[DEBUG] ' + Tools.escapeHTML(name) + '.</small></div>', preempt);
+			self.log('<div class="debug"><div class="chat"><small style="color:#999">[DEBUG] ' + Tools.escapeHTML(name) + '.</small></div></div>', preempt);
 			break;
 		case 'unlink':
 			break;
diff --git a/js/client-chat.js b/js/client-chat.js
index 3ea064cf8..3ad352d9e 100644
--- a/js/client-chat.js
+++ b/js/client-chat.js
@@ -449,6 +449,29 @@
 				}
 				return false;
 
+			case 'showdebug':
+				this.add('Debug battle messages: ON');
+				Tools.prefs('showdebug', true);
+				var debugStyle = $('#debugstyle').get(0);
+				var onCSS = '.debug {display: block;}';
+				if (!debugStyle) {
+					$('head').append('<style id="debugstyle">'+onCSS+'</style>');
+				} else {
+					debugStyle.innerHTML = onCSS;
+				}
+				return false;
+			case 'hidedebug':
+				this.add('Debug battle messages: HIDDEN');
+				Tools.prefs('showdebug', false);
+				var debugStyle = $('#debugstyle').get(0);
+				var offCSS = '.debug {display: none;}';
+				if (!debugStyle) {
+					$('head').append('<style id="debugstyle">'+offCSS+'</style>');
+				} else {
+					debugStyle.innerHTML = offCSS;
+				}
+				return false;
+
 			case 'showjoins':
 				this.add('Join/leave messages: ON');
 				Tools.prefs('showjoins', true);
diff --git a/js/client.js b/js/client.js
index 17a6b90e7..33849e7b7 100644
--- a/js/client.js
+++ b/js/client.js
@@ -267,6 +267,15 @@
 				if (musicVolume !== undefined) BattleSound.setBgmVolume(musicVolume);
 
 				if (Tools.prefs('logchat')) Storage.startLoggingChat();
+				if (Tools.prefs('showdebug')) {
+					var debugStyle = $('#debugstyle').get(0);
+					var onCSS = '.debug {display: block;}';
+					if (!debugStyle) {
+						$('head').append('<style id="debugstyle">'+onCSS+'</style>');
+					} else {
+						debugStyle.innerHTML = onCSS;
+					}
+				}
 			});
 
 			this.on('init:unsupported', function() {
diff --git a/style/client.css b/style/client.css
index a7f27a529..1a614d0f0 100644
--- a/style/client.css
+++ b/style/client.css
@@ -930,6 +930,9 @@ p.or:after {
 .chat.timer {
 	color: #992222;
 }
+.debug {
+	display: none;
+}
 .highlighted {
 	background-color: #FFDDAA;
 }