diff --git a/cmd-display-message.c b/cmd-display-message.c
index 07cd12a8..2e935908 100644
--- a/cmd-display-message.c
+++ b/cmd-display-message.c
@@ -39,8 +39,8 @@ const struct cmd_entry cmd_display_message_entry = {
 	.name = "display-message",
 	.alias = "display",
 
-	.args = { "c:pt:F:v", 0, 1 },
-	.usage = "[-pv] [-c target-client] [-F format] "
+	.args = { "ac:pt:F:v", 0, 1 },
+	.usage = "[-apv] [-c target-client] [-F format] "
 		 CMD_TARGET_PANE_USAGE " [message]",
 
 	.target = { 't', CMD_FIND_PANE, 0 },
@@ -49,6 +49,14 @@ const struct cmd_entry cmd_display_message_entry = {
 	.exec = cmd_display_message_exec
 };
 
+static void
+cmd_display_message_each(const char *key, const char *value, void *arg)
+{
+	struct cmdq_item	*item = arg;
+
+	cmdq_print(item, "%s=%s", key, value);
+}
+
 static enum cmd_retval
 cmd_display_message_exec(struct cmd *self, struct cmdq_item *item)
 {
@@ -91,6 +99,12 @@ cmd_display_message_exec(struct cmd *self, struct cmdq_item *item)
 	ft = format_create(item->client, item, FORMAT_NONE, flags);
 	format_defaults(ft, target_c, s, wl, wp);
 
+	if (args_has(args, 'a')) {
+		if (item != NULL)
+			format_each(ft, cmd_display_message_each, item);
+		return (CMD_RETURN_NORMAL);
+	}
+
 	msg = format_expand_time(ft, template);
 	if (args_has(self->args, 'p'))
 		cmdq_print(item, "%s", msg);
diff --git a/format.c b/format.c
index ea1372e7..0d1351ad 100644
--- a/format.c
+++ b/format.c
@@ -716,7 +716,9 @@ format_merge(struct format_tree *ft, struct format_tree *from)
 struct format_tree *
 format_create(struct client *c, struct cmdq_item *item, int tag, int flags)
 {
-	struct format_tree	*ft;
+	struct format_tree		 *ft;
+	const struct window_mode	**wm;
+	char				  tmp[64];
 
 	if (!event_initialized(&format_job_event)) {
 		evtimer_set(&format_job_event, format_job_timer, NULL);
@@ -743,6 +745,14 @@ format_create(struct client *c, struct cmdq_item *item, int tag, int flags)
 	format_add(ft, "socket_path", "%s", socket_path);
 	format_add_tv(ft, "start_time", &start_time);
 
+	for (wm = all_window_modes; *wm != NULL; wm++) {
+		if ((*wm)->default_format != NULL) {
+			xsnprintf(tmp, sizeof tmp, "%s_format", (*wm)->name);
+			tmp[strcspn(tmp, "-")] = '_';
+			format_add(ft, tmp, "%s", (*wm)->default_format);
+		}
+	}
+
 	if (item != NULL) {
 		if (item->cmd != NULL)
 			format_add(ft, "command", "%s", item->cmd->entry->name);
@@ -771,6 +781,30 @@ format_free(struct format_tree *ft)
 	free(ft);
 }
 
+/* Walk each format. */
+void
+format_each(struct format_tree *ft, void (*cb)(const char *, const char *,
+    void *), void *arg)
+{
+	struct format_entry	*fe;
+	static char		 s[64];
+
+	RB_FOREACH(fe, format_entry_tree, &ft->tree) {
+		if (fe->t != 0) {
+			xsnprintf(s, sizeof s, "%lld", (long long)fe->t);
+			cb(fe->key, fe->value, s);
+		} else {
+			if (fe->value == NULL && fe->cb != NULL) {
+				fe->cb(ft, fe);
+				if (fe->value == NULL)
+					fe->value = xstrdup("");
+			}
+			cb(fe->key, fe->value, arg);
+		}
+	}
+}
+
+
 /* Add a key-value pair. */
 void
 format_add(struct format_tree *ft, const char *key, const char *fmt, ...)
diff --git a/tmux.1 b/tmux.1
index aadf113b..de25d227 100644
--- a/tmux.1
+++ b/tmux.1
@@ -4282,7 +4282,7 @@ option.
 This command works only from inside
 .Nm .
 .It Xo Ic display-message
-.Op Fl pv
+.Op Fl apv
 .Op Fl c Ar target-client
 .Op Fl t Ar target-pane
 .Op Ar message
@@ -4305,9 +4305,10 @@ if
 is given, otherwise the active pane for the session attached to
 .Ar target-client .
 .Pp
-With
-.Fl v ,
-verbose logging is printed as the format is parsed.
+.Fl v
+prints verbose logging as the format is parsed and
+.Fl a
+lists the format variables and their values.
 .El
 .Sh BUFFERS
 .Nm
diff --git a/tmux.h b/tmux.h
index db45ac13..16727536 100644
--- a/tmux.h
+++ b/tmux.h
@@ -706,6 +706,7 @@ struct screen_write_ctx {
 struct window_mode_entry;
 struct window_mode {
 	const char	*name;
+	const char	*default_format;
 
 	struct screen	*(*init)(struct window_mode_entry *,
 			     struct cmd_find_state *, struct args *);
@@ -1589,6 +1590,8 @@ struct format_tree *format_create(struct client *, struct cmdq_item *, int,
 void		 format_free(struct format_tree *);
 void printflike(3, 4) format_add(struct format_tree *, const char *,
 		     const char *, ...);
+void		 format_each(struct format_tree *, void (*)(const char *,
+		     const char *, void *), void *);
 char		*format_expand_time(struct format_tree *, const char *);
 char		*format_expand(struct format_tree *, const char *);
 char		*format_single(struct cmdq_item *, const char *,
@@ -2158,6 +2161,7 @@ void	 screen_select_cell(struct screen *, struct grid_cell *,
 /* window.c */
 extern struct windows windows;
 extern struct window_pane_tree all_window_panes;
+extern const struct window_mode *all_window_modes[];
 int		 window_cmp(struct window *, struct window *);
 RB_PROTOTYPE(windows, window, entry, window_cmp);
 int		 winlink_cmp(struct winlink *, struct winlink *);
diff --git a/window-buffer.c b/window-buffer.c
index 379b90ad..79b02e9b 100644
--- a/window-buffer.c
+++ b/window-buffer.c
@@ -40,6 +40,7 @@ static void		 window_buffer_key(struct window_mode_entry *,
 
 const struct window_mode window_buffer_mode = {
 	.name = "buffer-mode",
+	.default_format = WINDOW_BUFFER_DEFAULT_FORMAT,
 
 	.init = window_buffer_init,
 	.free = window_buffer_free,
diff --git a/window-client.c b/window-client.c
index db1edbb3..ec98984d 100644
--- a/window-client.c
+++ b/window-client.c
@@ -42,6 +42,7 @@ static void		 window_client_key(struct window_mode_entry *,
 
 const struct window_mode window_client_mode = {
 	.name = "client-mode",
+	.default_format = WINDOW_CLIENT_DEFAULT_FORMAT,
 
 	.init = window_client_init,
 	.free = window_client_free,
diff --git a/window-tree.c b/window-tree.c
index c0d71a7e..55dda694 100644
--- a/window-tree.c
+++ b/window-tree.c
@@ -55,6 +55,7 @@ static void		 window_tree_key(struct window_mode_entry *,
 
 const struct window_mode window_tree_mode = {
 	.name = "tree-mode",
+	.default_format = WINDOW_TREE_DEFAULT_FORMAT,
 
 	.init = window_tree_init,
 	.free = window_tree_free,
diff --git a/window.c b/window.c
index 66806001..2f1049b2 100644
--- a/window.c
+++ b/window.c
@@ -60,6 +60,17 @@ static u_int	next_window_pane_id;
 static u_int	next_window_id;
 static u_int	next_active_point;
 
+/* List of window modes. */
+const struct window_mode *all_window_modes[] = {
+	&window_buffer_mode,
+	&window_client_mode,
+	&window_clock_mode,
+	&window_copy_mode,
+	&window_tree_mode,
+	&window_view_mode,
+	NULL
+};
+
 static void	window_destroy(struct window *);
 
 static struct window_pane *window_pane_create(struct window *, u_int, u_int,