diff --git a/extensions/Makefile.am b/extensions/Makefile.am
index b09e1824..634d4469 100644
--- a/extensions/Makefile.am
+++ b/extensions/Makefile.am
@@ -45,6 +45,7 @@ extension_LTLIBRARIES =		\
   sno_globaloper.la		\
   umode_noctcp.la		\
   m_adminwall.la		\
+  m_botmode.la			\
   m_echotags.la			\
   m_extendchans.la		\
   m_findforwards.la		\
diff --git a/extensions/m_botmode.c b/extensions/m_botmode.c
new file mode 100644
index 00000000..069f5916
--- /dev/null
+++ b/extensions/m_botmode.c
@@ -0,0 +1,100 @@
+/*
+ *  Copyright (C) 2021 David Schultz <me@zpld.me>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
+ *  USA
+ */
+
+#include "stdinc.h"
+#include "capability.h"
+#include "client.h"
+#include "hook.h"
+#include "ircd.h"
+#include "send.h"
+#include "logger.h"
+#include "modules.h"
+#include "msgbuf.h"
+#include "numeric.h"
+#include "supported.h"
+#include "s_conf.h"
+#include "s_serv.h"
+#include "s_user.h"
+#include "s_newconf.h"
+
+static char botmode_desc[] = "Provides support for the IRCv3 draft/bot spec";
+
+static void h_bm_outbound_msgbuf(void *);
+static void h_bm_whois(void *);
+
+static unsigned CLICAP_BOT;
+
+mapi_cap_list_av2 botmode_caps[] = {
+	{ MAPI_CAP_CLIENT, "draft/bot", NULL, &CLICAP_BOT },
+	{ 0, NULL, NULL, NULL},
+};
+
+mapi_hfn_list_av1 botmode_hfnlist[] = {
+	{ "outbound_msgbuf", h_bm_outbound_msgbuf, HOOK_NORMAL },
+	{ "doing_whois_global", h_bm_whois, HOOK_MONITOR },
+	{ "doing_whois", h_bm_whois, HOOK_MONITOR },
+	{ NULL, NULL, 0 }
+};
+
+static void
+h_bm_outbound_msgbuf(void *data_)
+{
+	hook_data *data = data_;
+	struct MsgBuf *msgbuf = data->arg1;
+
+	if (data->client->umodes & user_modes['B'])
+	{
+		msgbuf_append_tag(msgbuf, "draft/bot", NULL, CLICAP_BOT);
+	}
+}
+
+static void
+h_bm_whois(void *data_)
+{
+	hook_data_client *data = data_;
+	if (data->target->umodes & user_modes['B'])
+	{
+		sendto_one_numeric(data->client, RPL_WHOISBOT,
+			form_str(RPL_WHOISBOT), data->target->name, ServerInfo.network_name);
+	}
+}
+
+static int
+_modinit(void)
+{
+	user_modes['B'] = find_umode_slot();
+	construct_umodebuf();
+	if (!user_modes['B'])
+	{
+		ierror("m_botmode: unable to allocate usermode slot for +B, unloading extension");
+		return -1;
+	}
+	add_isupport("BOT", isupport_umode, "B");
+	return 0;
+}
+
+static void
+_moddeinit(void)
+{
+	user_modes['B'] = 0;
+	construct_umodebuf();
+	delete_isupport("BOT");
+}
+
+DECLARE_MODULE_AV2(botmode, _modinit, _moddeinit, NULL, NULL, botmode_hfnlist, botmode_caps, NULL, botmode_desc);
diff --git a/include/messages.h b/include/messages.h
index a50d9a6d..6112098a 100644
--- a/include/messages.h
+++ b/include/messages.h
@@ -107,6 +107,7 @@
 #define NUMERIC_STR_331      ":%s 331 %s %s :No topic is set."
 #define NUMERIC_STR_332      ":%s 332 %s %s :%s"
 #define NUMERIC_STR_333      ":%s 333 %s %s %s %lld"
+#define NUMERIC_STR_335      "%s :is a bot on %s"
 #define NUMERIC_STR_338      "%s %s :actually using host"
 #define NUMERIC_STR_341      ":%s 341 %s %s %s"
 #define NUMERIC_STR_346      ":%s 346 %s %s %s %s %lu"
diff --git a/include/numeric.h b/include/numeric.h
index 9132b7d1..06c59d71 100644
--- a/include/numeric.h
+++ b/include/numeric.h
@@ -160,6 +160,7 @@
 #define RPL_NOTOPIC          331
 #define RPL_TOPIC            332
 #define RPL_TOPICWHOTIME     333
+#define RPL_WHOISBOT         335
 #define RPL_WHOISACTUALLY    338
 
 #define RPL_INVITING         341