diff -pu dwm.hide_vacant_tags/config.def.h dwm.programtags+hidewithvacanttags/config.def.h
--- dwm.hide_vacant_tags/config.def.h	2021-03-15 16:37:24.586622415 -0500
+++ dwm.programtags+hidewithvacanttags/config.def.h	2021-03-15 16:32:37.586956549 -0500
@@ -21,6 +21,10 @@ static const char *colors[][3]      = {
 /* tagging */
 static const char *tags[] = { "1", "2", "3", "4", "5", "6", "7", "8", "9" };
 
+static const char ptagf[] = "[%s %s]";	/* format of a tag label */
+static const char etagf[] = "[%s]";	/* format of an empty tag */
+static const int lcaselbl = 0;		/* 1 means make tag label lowercase */	
+
 static const Rule rules[] = {
 	/* xprop(1):
 	 *	WM_CLASS(STRING) = instance, class
diff -pu dwm.hide_vacant_tags/dwm.c dwm.programtags+hidewithvacanttags/dwm.c
--- dwm.hide_vacant_tags/dwm.c	2021-03-15 16:37:38.189939908 -0500
+++ dwm.programtags+hidewithvacanttags/dwm.c	2021-03-15 16:32:23.693639390 -0500
@@ -20,6 +20,7 @@
  *
  * To understand everything else, start reading main().
  */
+#include <ctype.h> /* for making tab label lowercase, very tiny standard library */
 #include <errno.h>
 #include <locale.h>
 #include <signal.h>
@@ -272,6 +273,8 @@ static Window root, wmcheckwin;
 /* configuration, allows nested code to access above variables */
 #include "config.h"
 
+unsigned int tagw[LENGTH(tags)];
+
 /* compile-time check if all tags fit into an unsigned int bit array. */
 struct NumTags { char limitexceeded[LENGTH(tags) > 31 ? -1 : 1]; };
 
@@ -438,7 +441,7 @@ buttonpress(XEvent *e)
 			/* do not reserve space for vacant tags */
 			if (!(occ & 1 << i || m->tagset[m->seltags] & 1 << i))
 				continue;
-			x += TEXTW(tags[i]);
+			x += tagw[i];
 		} while (ev->x >= x && ++i < LENGTH(tags));
 		if (i < LENGTH(tags)) {
 			click = ClkTagBar;
@@ -706,6 +709,8 @@ drawbar(Monitor *m)
 	int boxw = drw->fonts->h / 6 + 2;
 	unsigned int i, occ = 0, urg = 0;
 	Client *c;
+	char tagdisp[64];
+	char *masterclientontag[LENGTH(tags)];
 
 	/* draw status first so it can be overdrawn by tags later */
 	if (m == selmon) { /* status is only drawn on selected monitor */
@@ -714,10 +719,21 @@ drawbar(Monitor *m)
 		drw_text(drw, m->ww - tw, 0, tw, bh, 0, stext, 0);
 	}
 
+	for (i = 0; i < LENGTH(tags); i++)
+		masterclientontag[i] = NULL;
+
 	for (c = m->clients; c; c = c->next) {
 		occ |= c->tags == 255 ? 0 : c->tags;
 		if (c->isurgent)
 			urg |= c->tags;
+		for (i = 0; i < LENGTH(tags); i++)
+			if (!masterclientontag[i] && c->tags & (1<<i)) {
+				XClassHint ch = { NULL, NULL };
+				XGetClassHint(dpy, c->win, &ch);
+				masterclientontag[i] = ch.res_class;
+				if (lcaselbl)
+					masterclientontag[i][0] = tolower(masterclientontag[i][0]);
+			}
 	}
 	x = 0;
 	for (i = 0; i < LENGTH(tags); i++) {
@@ -725,9 +741,14 @@ drawbar(Monitor *m)
 		if (!(occ & 1 << i || m->tagset[m->seltags] & 1 << i))
 		continue;
 
-		w = TEXTW(tags[i]);
+		if (masterclientontag[i])
+			snprintf(tagdisp, 64, ptagf, tags[i], masterclientontag[i]);
+		else
+			snprintf(tagdisp, 64, etagf, tags[i]);
+		masterclientontag[i] = tagdisp;
+		tagw[i] = w = TEXTW(masterclientontag[i]);
 		drw_setscheme(drw, scheme[m->tagset[m->seltags] & 1 << i ? SchemeSel : SchemeNorm]);
-		drw_text(drw, x, 0, w, bh, lrpad / 2, tags[i], urg & 1 << i);
+		drw_text(drw, x, 0, w, bh, lrpad / 2, masterclientontag[i], urg & 1 << i);
 		x += w;
 	}
 	w = blw = TEXTW(m->ltsymbol);