diff --git a/README.md b/README.md
index 6f8fbe43..6536a65c 100644
--- a/README.md
+++ b/README.md
@@ -43,6 +43,7 @@ Assuming you already have all the usual building tools installed (e.g. gcc, meso
 * libGL (optional, disable with the `-Dopengl=false` meson configure flag)
 * libpcre (optional, disable with the `-Dregex=false` meson configure flag)
 * libev
+* uthash
 
 To build the documents, you need `asciidoc`
 
diff --git a/meson.build b/meson.build
index 6fe5e1b0..ff25fab9 100644
--- a/meson.build
+++ b/meson.build
@@ -31,6 +31,9 @@ if get_option('sanitize')
 	endif
 	add_global_arguments('-fsanitize='+','.join(sanitizers), language: 'c')
 	add_global_link_arguments('-fsanitize='+','.join(sanitizers), language: 'c')
+	if cc.has_argument('-fno-sanitize=unsigned-integer-overflow')
+		add_global_arguments('-fno-sanitize=unsigned-integer-overflow', language: 'c')
+	endif
 endif
 
 if get_option('modularize')
diff --git a/src/common.h b/src/common.h
index 407d0bb9..f889633f 100644
--- a/src/common.h
+++ b/src/common.h
@@ -49,6 +49,7 @@
 #include <xcb/sync.h>
 #include <xcb/xinerama.h>
 
+#include "uthash_extra.h"
 #ifdef CONFIG_OPENGL
 // libGL
 #include "backend/gl/glx.h"
@@ -389,8 +390,10 @@ typedef struct session {
 	int n_expose;
 
 	// === Window related ===
-	/// Linked list of all windows.
-	win *list;
+	/// A hash table of all windows.
+	win *windows;
+	/// Windows in their stacking order
+	win *window_stack;
 	/// Pointer to <code>win</code> of current active window. Used by
 	/// EWMH <code>_NET_ACTIVE_WINDOW</code> focus detection. In theory,
 	/// it's more reliable to store the window ID directly here, just in
@@ -732,43 +735,6 @@ static inline xcb_window_t get_tgt_window(session_t *ps) {
 	return ps->overlay != XCB_NONE ? ps->overlay : ps->root;
 }
 
-/**
- * Find a window from window id in window linked list of the session.
- */
-static inline win *find_win(session_t *ps, xcb_window_t id) {
-	if (!id)
-		return NULL;
-
-	win *w;
-
-	for (w = ps->list; w; w = w->next) {
-		if (w->id == id && w->state != WSTATE_DESTROYING) {
-			return w;
-		}
-	}
-
-	return 0;
-}
-
-/**
- * Find out the WM frame of a client window using existing data.
- *
- * @param id window ID
- * @return struct win object of the found window, NULL if not found
- */
-static inline win *find_toplevel(session_t *ps, xcb_window_t id) {
-	if (!id)
-		return NULL;
-
-	for (win *w = ps->list; w; w = w->next) {
-		if (w->client_win == id && w->state != WSTATE_DESTROYING) {
-			return w;
-		}
-	}
-
-	return NULL;
-}
-
 /**
  * Check if current backend uses GLX.
  */
diff --git a/src/compton.c b/src/compton.c
index a4e3ce3a..5a26a793 100644
--- a/src/compton.c
+++ b/src/compton.c
@@ -51,6 +51,7 @@
 #endif
 #include "event.h"
 #include "options.h"
+#include "uthash_extra.h"
 
 /// Get session_t pointer from a pointer to a member of session_t
 #define session_ptr(ptr, member)                                                         \
@@ -419,7 +420,7 @@ static void handle_root_flags(session_t *ps) {
 static win *paint_preprocess(session_t *ps, bool *fade_running) {
 	// XXX need better, more general name for `fade_running`. It really
 	// means if fade is still ongoing after the current frame is rendered
-	win *t = NULL, *next = NULL;
+	win *t = NULL;
 	*fade_running = false;
 
 	// Fading step calculation
@@ -436,8 +437,7 @@ static win *paint_preprocess(session_t *ps, bool *fade_running) {
 	ps->fade_time += steps * ps->o.fade_delta;
 
 	// First, let's process fading
-	for (win *w = ps->list; w; w = next) {
-		next = w->next;
+	WIN_STACK_ITER(ps, w) {
 		const winmode_t mode_old = w->mode;
 		const bool was_painted = w->to_paint;
 		const double opacity_old = w->opacity;
@@ -490,15 +490,12 @@ static win *paint_preprocess(session_t *ps, bool *fade_running) {
 	// Track whether it's the highest window to paint
 	bool is_highest = true;
 	bool reg_ignore_valid = true;
-	for (win *w = ps->list; w; w = next) {
+	WIN_STACK_ITER(ps, w) {
 		__label__ skip_window;
 		bool to_paint = true;
 		// w->to_paint remembers whether this window is painted last time
 		const bool was_painted = w->to_paint;
 
-		// In case calling the fade callback function destroys this window
-		next = w->next;
-
 		// Destroy reg_ignore if some window above us invalidated it
 		if (!reg_ignore_valid) {
 			rc_region_unref(&w->reg_ignore);
@@ -672,7 +669,7 @@ static void restack_win(session_t *ps, win *w, xcb_window_t new_above) {
 		win **prev = NULL, **prev_old = NULL;
 
 		bool found = false;
-		for (prev = &ps->list; *prev; prev = &(*prev)->next) {
+		for (prev = &ps->window_stack; *prev; prev = &(*prev)->next) {
 			if ((*prev)->id == new_above && (*prev)->state != WSTATE_DESTROYING) {
 				found = true;
 				break;
@@ -685,7 +682,7 @@ static void restack_win(session_t *ps, win *w, xcb_window_t new_above) {
 			return;
 		}
 
-		for (prev_old = &ps->list; *prev_old; prev_old = &(*prev_old)->next) {
+		for (prev_old = &ps->window_stack; *prev_old; prev_old = &(*prev_old)->next) {
 			if ((*prev_old) == w) {
 				break;
 			}
@@ -713,8 +710,7 @@ static void restack_win(session_t *ps, win *w, xcb_window_t new_above) {
 
 /// Free up all the images and deinit the backend
 static void destroy_backend(session_t *ps) {
-	for (win *w = ps->list, *next; w; w = next) {
-		next = w->next;
+	WIN_STACK_ITER(ps, w) {
 		// Wrapping up fading in progress
 		win_skip_fading(ps, &w);
 
@@ -760,7 +756,9 @@ static bool initialize_backend(session_t *ps) {
 			return false;
 		}
 
-		for (win *w = ps->list; w; w = w->next) {
+		// window_stack shouldn't include window that's not in the hash table at
+		// this point. Since there cannot be any fading windows.
+		HASH_ITER2(ps->windows, w) {
 			if (w->a.map_state == XCB_MAP_STATE_VIEWABLE) {
 				if (!win_bind_image(ps, w)) {
 					w->flags |= WIN_FLAGS_IMAGE_ERROR;
@@ -800,8 +798,8 @@ void configure_root(session_t *ps, int width, int height) {
 	ps->damage = ps->damage_ring + ps->ndamage - 1;
 
 	// Invalidate reg_ignore from the top
-	rc_region_unref(&ps->list->reg_ignore);
-	ps->list->reg_ignore_valid = false;
+	rc_region_unref(&ps->window_stack->reg_ignore);
+	ps->window_stack->reg_ignore_valid = false;
 
 #ifdef CONFIG_OPENGL
 	// GLX root change callback
@@ -846,7 +844,6 @@ void configure_win(session_t *ps, xcb_configure_notify_event_t *ce) {
 		restack_win(ps, w, ce->above_sibling);
 	} else {
 		restack_win(ps, w, ce->above_sibling);
-
 		bool factor_change = false;
 		win_extents(w, &damage);
 
@@ -897,7 +894,7 @@ void circulate_win(session_t *ps, xcb_circulate_notify_event_t *ce) {
 		return;
 
 	if (ce->place == PlaceOnTop) {
-		new_above = ps->list->id;
+		new_above = ps->window_stack->id;
 	} else {
 		new_above = XCB_NONE;
 	}
@@ -1017,12 +1014,14 @@ void opts_init_track_focus(session_t *ps) {
 
 	if (!ps->o.use_ewmh_active_win) {
 		// Start listening to FocusChange events
-		for (win *w = ps->list; w; w = w->next)
-			if (w->a.map_state == XCB_MAP_STATE_VIEWABLE)
+		HASH_ITER2(ps->windows, w) {
+			if (w->a.map_state == XCB_MAP_STATE_VIEWABLE) {
 				xcb_change_window_attributes(
 				    ps->c, w->id, XCB_CW_EVENT_MASK,
 				    (const uint32_t[]){
 				        determine_evmask(ps, w->id, WIN_EVMODE_FRAME)});
+			}
+		}
 	}
 
 	// Recheck focus
@@ -1687,7 +1686,7 @@ static session_t *session_init(int argc, char **argv, Display *dpy,
 	    .size_expose = 0,
 	    .n_expose = 0,
 
-	    .list = NULL,
+	    .windows = NULL,
 	    .active_win = NULL,
 	    .active_leader = XCB_NONE,
 
@@ -2125,15 +2124,15 @@ static session_t *session_init(int argc, char **argv, Display *dpy,
 			add_win(ps, children[i], i ? children[i - 1] : XCB_NONE);
 		}
 
-		for (win *i = ps->list; i; i = i->next) {
-			if (i->a.map_state == XCB_MAP_STATE_VIEWABLE) {
-				map_win(ps, i);
+		HASH_ITER2(ps->windows, w) {
+			if (w->a.map_state == XCB_MAP_STATE_VIEWABLE) {
+				map_win(ps, w);
 			}
 		}
 
 		free(reply);
 		log_trace("Initial stack:");
-		for (win *c = ps->list; c; c = c->next) {
+		for (win *c = ps->window_stack; c; c = c->next) {
 			log_trace("%#010x \"%s\"", c->id, c->name);
 		}
 	}
@@ -2183,22 +2182,17 @@ static void session_destroy(session_t *ps) {
 #endif
 
 	// Free window linked list
-	{
-		win *next = NULL;
-		win *list = ps->list;
-		ps->list = NULL;
 
-		for (win *w = list; w; w = next) {
-			next = w->next;
-
-			if (w->state != WSTATE_DESTROYING) {
-				win_ev_stop(ps, w);
-			}
-
-			free_win_res(ps, w);
-			free(w);
+	WIN_STACK_ITER(ps, w) {
+		if (w->state != WSTATE_DESTROYING) {
+			win_ev_stop(ps, w);
+			HASH_DEL(ps->windows, w);
 		}
+
+		free_win_res(ps, w);
+		free(w);
 	}
+	ps->window_stack = NULL;
 
 	// Free blacklists
 	free_wincondlst(&ps->o.shadow_blacklist);
diff --git a/src/dbus.c b/src/dbus.c
index 01f1d45e..18f74cb7 100644
--- a/src/dbus.c
+++ b/src/dbus.c
@@ -26,6 +26,7 @@
 #include "types.h"
 #include "utils.h"
 #include "win.h"
+#include "uthash_extra.h"
 
 #include "dbus.h"
 
@@ -465,10 +466,9 @@ static bool cdbus_apdarg_string(session_t *ps, DBusMessage *msg, const void *dat
 static bool cdbus_apdarg_wids(session_t *ps, DBusMessage *msg, const void *data) {
 	// Get the number of wids we are to include
 	unsigned count = 0;
-	for (win *w = ps->list; w; w = w->next) {
-		if (w->state != WSTATE_DESTROYING) {
-			++count;
-		}
+	HASH_ITER2(ps->windows, w) {
+		assert(w->state != WSTATE_DESTROYING);
+		++count;
 	}
 
 	if (!count) {
@@ -480,17 +480,13 @@ static bool cdbus_apdarg_wids(session_t *ps, DBusMessage *msg, const void *data)
 	auto arr = ccalloc(count, cdbus_window_t);
 
 	// Build the array
-	{
-		cdbus_window_t *pcur = arr;
-		for (win *w = ps->list; w; w = w->next) {
-			if (w->state != WSTATE_DESTROYING) {
-				*pcur = w->id;
-				++pcur;
-				assert(pcur <= arr + count);
-			}
-		}
-		assert(pcur == arr + count);
+	cdbus_window_t *pcur = arr;
+	HASH_ITER2(ps->windows, w) {
+		assert(w->state != WSTATE_DESTROYING);
+		*pcur = w->id;
+		++pcur;
 	}
+	assert(pcur == arr + count);
 
 	// Append arguments
 	if (!dbus_message_append_args(msg, DBUS_TYPE_ARRAY, CDBUS_TYPE_WINDOW, &arr,
diff --git a/src/meson.build b/src/meson.build
index 44b34173..d22f1da0 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -23,6 +23,10 @@ foreach i : required_package
 	base_deps += [dependency(i, required: true)]
 endforeach
 
+if not cc.has_header('uthash.h')
+  error('Dependency uthash not found')
+endif
+
 deps = []
 
 if get_option('config_file')
diff --git a/src/opengl.c b/src/opengl.c
index 65f339d0..08563a3d 100644
--- a/src/opengl.c
+++ b/src/opengl.c
@@ -26,6 +26,7 @@
 #include "string_utils.h"
 #include "utils.h"
 #include "win.h"
+#include "uthash_extra.h"
 
 #include "opengl.h"
 
@@ -220,8 +221,9 @@ void glx_destroy(session_t *ps) {
 		return;
 
 	// Free all GLX resources of windows
-	for (win *w = ps->list; w; w = w->next)
+	WIN_STACK_ITER(ps, w) {
 		free_win_res_glx(ps, w);
+	}
 
 	// Free GLSL shaders/programs
 	for (int i = 0; i < MAX_BLUR_PASS; ++i) {
diff --git a/src/uthash_extra.h b/src/uthash_extra.h
new file mode 100644
index 00000000..cbc10561
--- /dev/null
+++ b/src/uthash_extra.h
@@ -0,0 +1,7 @@
+#pragma once
+
+#include <uthash.h>
+
+#define HASH_ITER2(head, el)                                                             \
+	for (__typeof__(head) el = (head), __tmp = el != NULL ? el->hh.next : NULL;      \
+	     el != NULL; el = __tmp, __tmp = el != NULL ? el->hh.next : NULL)
diff --git a/src/win.c b/src/win.c
index 3a094b2b..8970d344 100644
--- a/src/win.c
+++ b/src/win.c
@@ -25,6 +25,7 @@
 #include "render.h"
 #include "string_utils.h"
 #include "types.h"
+#include "uthash_extra.h"
 #include "utils.h"
 #include "x.h"
 
@@ -56,8 +57,9 @@
  * Clear leader cache of all windows.
  */
 static inline void clear_cache_win_leaders(session_t *ps) {
-	for (win *w = ps->list; w; w = w->next)
+	for (win *w = ps->window_stack; w; w = w->next) {
 		w->cache_leader = XCB_NONE;
+	}
 }
 
 static inline void wid_set_opacity_prop(session_t *ps, xcb_window_t wid, opacity_t val) {
@@ -79,9 +81,11 @@ static inline void group_update_focused(session_t *ps, xcb_window_t leader) {
 	if (!leader)
 		return;
 
-	for (win *w = ps->list; w; w = w->next) {
-		if (win_get_leader(ps, w) == leader && w->state != WSTATE_DESTROYING)
+	HASH_ITER2(ps->windows, w) {
+		assert(w->state != WSTATE_DESTROYING);
+		if (win_get_leader(ps, w) == leader) {
 			win_update_focused(ps, w);
+		}
 	}
 
 	return;
@@ -97,10 +101,11 @@ static inline bool group_is_focused(session_t *ps, xcb_window_t leader) {
 	if (!leader)
 		return false;
 
-	for (win *w = ps->list; w; w = w->next) {
-		if (win_get_leader(ps, w) == leader && w->state != WSTATE_DESTROYING &&
-		    win_is_focused_real(ps, w))
+	HASH_ITER2(ps->windows, w) {
+		assert(w->state != WSTATE_DESTROYING);
+		if (win_get_leader(ps, w) == leader && win_is_focused_real(ps, w)) {
 			return true;
+		}
 	}
 
 	return false;
@@ -1022,15 +1027,16 @@ void add_win(session_t *ps, xcb_window_t id, xcb_window_t prev) {
 	// Find window insertion point
 	win **p = NULL;
 	if (prev) {
-		for (p = &ps->list; *p; p = &(*p)->next) {
+		for (p = &ps->window_stack; *p; p = &(*p)->next) {
 			if ((*p)->id == prev && (*p)->state != WSTATE_DESTROYING)
 				break;
 		}
 	} else {
-		p = &ps->list;
+		p = &ps->window_stack;
 	}
 	new->next = *p;
 	*p = new;
+	HASH_ADD_INT(ps->windows, id, new);
 
 #ifdef CONFIG_DBUS
 	// Send D-Bus signal
@@ -1414,7 +1420,7 @@ void win_update_frame_extents(session_t *ps, win *w, xcb_window_t client) {
 }
 
 bool win_is_region_ignore_valid(session_t *ps, const win *w) {
-	for (win *i = ps->list; w; w = w->next) {
+	WIN_STACK_ITER(ps, i) {
 		if (i == w)
 			break;
 		if (!i->reg_ignore_valid)
@@ -1481,7 +1487,7 @@ static void finish_destroy_win(session_t *ps, win **_w) {
 	}
 
 	log_trace("Trying to destroy (%#010x)", w->id);
-	for (prev = &ps->list; *prev; prev = &(*prev)->next) {
+	for (prev = &ps->window_stack; *prev; prev = &(*prev)->next) {
 		if (w == *prev) {
 			log_trace("Found (%#010x \"%s\")", w->id, w->name);
 			*prev = w->next;
@@ -1495,7 +1501,7 @@ static void finish_destroy_win(session_t *ps, win **_w) {
 			// Drop w from all prev_trans to avoid accessing freed memory in
 			// repair_win()
 			// TODO there can only be one prev_trans pointing to w
-			for (win *w2 = ps->list; w2; w2 = w2->next) {
+			for (win *w2 = ps->window_stack; w2; w2 = w2->next) {
 				if (w == w2->prev_trans) {
 					w2->prev_trans = NULL;
 				}
@@ -1545,6 +1551,15 @@ void unmap_win(session_t *ps, win **_w, bool destroy) {
 		return;
 	}
 
+	if (destroy) {
+		// Delete destroyed window from the hash table, so future window with the
+		// same window id won't confuse us.
+		// Keep the window in the window stack, since we might still need to
+		// render it (fading out). Window will be removed from the stack when
+		// fading finishes.
+		HASH_DEL(ps->windows, w);
+	}
+
 	if (unlikely(w->state == WSTATE_UNMAPPED) || w->a._class == XCB_WINDOW_CLASS_INPUT_ONLY) {
 		if (unlikely(!destroy)) {
 			log_warn("Unmapping an already unmapped window %#010x %s twice",
@@ -1811,3 +1826,38 @@ void map_win_by_id(session_t *ps, xcb_window_t id) {
 
 	map_win(ps, w);
 }
+
+/**
+ * Find a window from window id in window linked list of the session.
+ */
+win *find_win(session_t *ps, xcb_window_t id) {
+	if (!id) {
+		return NULL;
+	}
+
+	win *w = NULL;
+	HASH_FIND_INT(ps->windows, &id, w);
+	assert(w == NULL || w->state != WSTATE_DESTROYING);
+	return w;
+}
+
+/**
+ * Find out the WM frame of a client window using existing data.
+ *
+ * @param id window ID
+ * @return struct win object of the found window, NULL if not found
+ */
+win *find_toplevel(session_t *ps, xcb_window_t id) {
+	if (!id) {
+		return NULL;
+	}
+
+	HASH_ITER2(ps->windows, w) {
+		assert(w->state != WSTATE_DESTROYING);
+		if (w->client_win == id) {
+			return w;
+		}
+	}
+
+	return NULL;
+}
diff --git a/src/win.h b/src/win.h
index e0e253d9..c1376540 100644
--- a/src/win.h
+++ b/src/win.h
@@ -7,20 +7,25 @@
 #include <xcb/render.h>
 #include <xcb/xcb.h>
 
+#include "uthash_extra.h"
+
 // FIXME shouldn't need this
 #ifdef CONFIG_OPENGL
 #include <GL/gl.h>
 #endif
 
+#include "backend/backend.h"
 #include "c2.h"
 #include "compiler.h"
 #include "region.h"
 #include "render.h"
 #include "types.h"
 #include "utils.h"
-#include "backend/backend.h"
 #include "x.h"
 
+#define WIN_STACK_ITER(ps, w)                                                            \
+	for (win *w = ps->window_stack, *next; w ? (next = w->next, true) : false; w = next)
+
 typedef struct session session_t;
 typedef struct _glx_texture glx_texture_t;
 
@@ -285,6 +290,7 @@ struct win {
 	/// Textures and FBO background blur use.
 	glx_blur_cache_t glx_blur_cache;
 #endif
+	UT_hash_handle hh;
 };
 
 void win_release_image(backend_t *base, win *w);
@@ -392,6 +398,8 @@ void win_ev_stop(session_t *ps, const win *w);
 /// Skip the current in progress fading of window,
 /// transition the window straight to its end state
 void win_skip_fading(session_t *ps, win **_w);
+win *find_win(session_t *ps, xcb_window_t id);
+win *find_toplevel(session_t *ps, xcb_window_t id);
 
 /**
  * Get the leader of a window.