diff -up a/config.def.h b/config.def.h
--- a/config.def.h	2022-10-04 19:38:18.000000000 +0200
+++ b/config.def.h	2023-05-06 22:19:27.298742237 +0200
@@ -5,6 +5,7 @@ static const unsigned int borderpx  = 1;
 static const unsigned int snap      = 32;       /* snap pixel */
 static const int showbar            = 1;        /* 0 means no bar */
 static const int topbar             = 1;        /* 0 means bottom bar */
+static const int allowkill          = 1;        /* allow killing clients by default? */
 static const char *fonts[]          = { "monospace:size=10" };
 static const char dmenufont[]       = "monospace:size=10";
 static const char col_gray1[]       = "#222222";
@@ -26,9 +27,9 @@ static const Rule rules[] = {
 	 *	WM_CLASS(STRING) = instance, class
 	 *	WM_NAME(STRING) = title
 	 */
-	/* class      instance    title       tags mask     isfloating   monitor */
-	{ "Gimp",     NULL,       NULL,       0,            1,           -1 },
-	{ "Firefox",  NULL,       NULL,       1 << 8,       0,           -1 },
+	/* class      instance    title       tags mask     allowkill    isfloating   monitor */
+	{ "Gimp",     NULL,       NULL,       0,            1,           1,           -1 },
+	{ "Firefox",  NULL,       NULL,       1 << 8,       1,           0,           -1 },
 };

 /* layout(s) */
@@ -78,6 +79,7 @@ static const Key keys[] = {
 	{ MODKEY,                       XK_m,      setlayout,      {.v = &layouts[2]} },
 	{ MODKEY,                       XK_space,  setlayout,      {0} },
 	{ MODKEY|ShiftMask,             XK_space,  togglefloating, {0} },
+    { MODKEY,                       XK_q,      toggleallowkill,{0} },
 	{ MODKEY,                       XK_0,      view,           {.ui = ~0 } },
 	{ MODKEY|ShiftMask,             XK_0,      tag,            {.ui = ~0 } },
 	{ MODKEY,                       XK_comma,  focusmon,       {.i = -1 } },
diff -up a/dwm.c b/dwm.c
--- a/dwm.c	2022-10-04 19:38:18.000000000 +0200
+++ b/dwm.c	2023-05-06 22:18:43.239357744 +0200
@@ -93,6 +93,7 @@ struct Client {
 	int bw, oldbw;
 	unsigned int tags;
 	int isfixed, isfloating, isurgent, neverfocus, oldstate, isfullscreen;
+    int allowkill;
 	Client *next;
 	Client *snext;
 	Monitor *mon;
@@ -137,6 +138,7 @@ typedef struct {
 	const char *instance;
 	const char *title;
 	unsigned int tags;
+    int allowkill;
 	int isfloating;
 	int monitor;
 } Rule;
@@ -212,6 +214,7 @@ static void tagmon(const Arg *arg);
 static void tile(Monitor *m);
 static void togglebar(const Arg *arg);
 static void togglefloating(const Arg *arg);
+static void toggleallowkill(const Arg *arg);
 static void toggletag(const Arg *arg);
 static void toggleview(const Arg *arg);
 static void unfocus(Client *c, int setfocus);
@@ -288,6 +291,7 @@ applyrules(Client *c)
 	/* rule matching */
 	c->isfloating = 0;
 	c->tags = 0;
+    c->allowkill = allowkill;
 	XGetClassHint(dpy, c->win, &ch);
 	class    = ch.res_class ? ch.res_class : broken;
 	instance = ch.res_name  ? ch.res_name  : broken;
@@ -300,6 +304,7 @@ applyrules(Client *c)
 		{
 			c->isfloating = r->isfloating;
 			c->tags |= r->tags;
+            c->allowkill = r->allowkill;
 			for (m = mons; m && m->num != r->monitor; m = m->next);
 			if (m)
 				c->mon = m;
@@ -1006,7 +1011,7 @@ keypress(XEvent *e)
 void
 killclient(const Arg *arg)
 {
-	if (!selmon->sel)
+	if (!selmon->sel || !selmon->sel->allowkill)
 		return;
 	if (!sendevent(selmon->sel, wmatom[WMDelete])) {
 		XGrabServer(dpy);
@@ -1704,6 +1709,13 @@ togglebar(const Arg *arg)
 }

 void
+toggleallowkill(const Arg *arg)
+{
+    if (!selmon->sel) return;
+    selmon->sel->allowkill = !selmon->sel->allowkill;
+}
+
+void
 togglefloating(const Arg *arg)
 {
 	if (!selmon->sel)