diff --git a/format.c b/format.c
index 3b58bde3..2d9c6a36 100644
--- a/format.c
+++ b/format.c
@@ -2262,6 +2262,38 @@ format_cb_pane_pipe_pid(struct format_tree *ft)
 	return (value);
 }
 
+/* Callback for pane_pb_progress. */
+static void *
+format_cb_pane_pb_progress(struct format_tree *ft)
+{
+	char    *value = NULL;
+
+	if (ft->wp != NULL)
+		xasprintf(&value, "%d", ft->wp->base.progress_bar.progress);
+	return (value);
+}
+
+/* Callback for pane_pb_state. */
+static void *
+format_cb_pane_pb_state(struct format_tree *ft)
+{
+	if (ft->wp != NULL) {
+		switch (ft->wp->base.progress_bar.state) {
+		case PROGRESS_BAR_HIDDEN:
+			return xstrdup("hidden");
+		case PROGRESS_BAR_NORMAL:
+			return xstrdup("normal");
+		case PROGRESS_BAR_ERROR:
+			return xstrdup("error");
+		case PROGRESS_BAR_INDETERMINATE:
+			return xstrdup("indeterminate");
+		case PROGRESS_BAR_PAUSED:
+			return xstrdup("paused");
+		}
+	}
+	return (NULL);
+}
+
 /* Callback for pane_right. */
 static void *
 format_cb_pane_right(struct format_tree *ft)
@@ -3349,6 +3381,12 @@ static const struct format_table_entry format_table[] = {
 	{ "pane_path", FORMAT_TABLE_STRING,
 	  format_cb_pane_path
 	},
+	{ "pane_pb_progress", FORMAT_TABLE_STRING,
+	  format_cb_pane_pb_progress
+	},
+	{ "pane_pb_state", FORMAT_TABLE_STRING,
+	  format_cb_pane_pb_state
+	},
 	{ "pane_pid", FORMAT_TABLE_STRING,
 	  format_cb_pane_pid
 	},
diff --git a/input.c b/input.c
index 707328dc..671f5788 100644
--- a/input.c
+++ b/input.c
@@ -164,6 +164,7 @@ static void	input_reset_cell(struct input_ctx *);
 static void	input_report_current_theme(struct input_ctx *);
 static void	input_osc_4(struct input_ctx *, const char *);
 static void	input_osc_8(struct input_ctx *, const char *);
+static void	input_osc_9(struct input_ctx *, const char *);
 static void	input_osc_10(struct input_ctx *, const char *);
 static void	input_osc_11(struct input_ctx *, const char *);
 static void	input_osc_12(struct input_ctx *, const char *);
@@ -2673,6 +2674,9 @@ input_exit_osc(struct input_ctx *ictx)
 	case 8:
 		input_osc_8(ictx, p);
 		break;
+	case 9:
+		input_osc_9(ictx, p);
+		break;
 	case 10:
 		input_osc_10(ictx, p);
 		break;
@@ -2941,6 +2945,57 @@ bad:
 	free(id);
 }
 
+/* Helper to handle setting the progress bar and redrawing. */
+static void
+input_set_progress_bar(struct input_ctx *ictx, enum progress_bar_state state,
+    int p)
+{
+	screen_set_progress_bar(ictx->ctx.s, state, p);
+ 	if (ictx->wp != NULL) {
+		server_redraw_window_borders(ictx->wp->window);
+		server_status_window(ictx->wp->window);
+	}
+}
+
+/* Handle the OSC 9;4 sequence for progress bars. */
+static void
+input_osc_9(struct input_ctx *ictx, const char *p)
+{
+	const char		*pb = p;
+	enum progress_bar_state	 state;
+	int			 progress = 0;
+
+	if (*pb++ != '4')
+		return;
+	if (*pb == '\0' || (*pb == ';' && pb[1] == '\0'))
+		return;
+
+	if (*pb++ != ';')
+		return;
+	if (*pb < '0' || *pb > '4')
+		goto bad;
+	state = *pb++ - '0';
+
+	if (*pb == '\0' || (*pb == ';' && pb[1] == '\0')) {
+		input_set_progress_bar(ictx, state, -1);
+		return;
+	}
+
+	if (*pb++ != ';')
+		goto bad;
+	while (*pb >= '0' && *pb <= '9') {
+		if (progress > 100)
+			goto bad;
+		progress = progress * 10 + *pb++ - '0';
+	}
+	if (*pb != '\0' || progress < 0 || progress > 100)
+		goto bad;
+	input_set_progress_bar(ictx, state, progress);
+	return;
+
+bad:
+	log_debug("bad OSC 9;4 %s", p);
+}
 
 /* Handle the OSC 10 sequence for setting and querying foreground colour. */
 static void
@@ -3151,7 +3206,7 @@ input_osc_52_parse(struct input_ctx *ictx, const char *p, u_char **out,
 		return (0);
 	}
 
-	len = (strlen(end) / 4) * 3;
+	len = ((strlen(end) + 3) / 4) * 3;
 	if (len == 0)
 		return (0);
 
diff --git a/screen.c b/screen.c
index a07a8e8c..8a9fa178 100644
--- a/screen.c
+++ b/screen.c
@@ -131,6 +131,7 @@ screen_reinit(struct screen *s)
 	image_free_all(s);
 #endif
 
+	screen_set_progress_bar(s, PROGRESS_BAR_HIDDEN, 0);
 	screen_reset_hyperlinks(s);
 }
 
@@ -296,6 +297,19 @@ screen_pop_title(struct screen *s)
 	}
 }
 
+/*
+ * Set the progress bar state and progress. The progress will not be updated
+ * if p is negative.
+ */
+void
+screen_set_progress_bar(struct screen *s, enum progress_bar_state pbs, int p)
+{
+	s->progress_bar.state = pbs;
+	if (p >= 0 && pbs != PROGRESS_BAR_INDETERMINATE)
+		s->progress_bar.progress = p;
+}
+
+
 /* Resize screen with options. */
 void
 screen_resize_cursor(struct screen *s, u_int sx, u_int sy, int reflow,
diff --git a/tmux.1 b/tmux.1
index a643b64e..d7a33038 100644
--- a/tmux.1
+++ b/tmux.1
@@ -6382,6 +6382,8 @@ The following variables are available, where appropriate:
 .It Li "pane_pid" Ta "" Ta "PID of first process in pane"
 .It Li "pane_pipe" Ta "" Ta "1 if pane is being piped"
 .It Li "pane_pipe_pid" Ta "" Ta "PID of pipe process, if any"
+.It Li "pane_pb_state" Ta "" Ta "Pane progress bar state, one of hidden, normal, error, indeterminate, paused (can be set by application)"
+.It Li "pane_pb_progress" Ta "" Ta "Pane progress bar progress percentage (can be set by application)"
 .It Li "pane_right" Ta "" Ta "Right of pane"
 .It Li "pane_search_string" Ta "" Ta "Last search string in copy mode"
 .It Li "pane_start_command" Ta "" Ta "Command pane started with"
diff --git a/tmux.h b/tmux.h
index f42dec56..4290576c 100644
--- a/tmux.h
+++ b/tmux.h
@@ -947,6 +947,20 @@ enum screen_cursor_style {
 	SCREEN_CURSOR_BAR
 };
 
+
+/* Progress bar, OSC 9;4. */
+enum progress_bar_state {
+	PROGRESS_BAR_HIDDEN = 0,
+	PROGRESS_BAR_NORMAL = 1,
+	PROGRESS_BAR_ERROR = 2,
+	PROGRESS_BAR_INDETERMINATE = 3,
+	PROGRESS_BAR_PAUSED = 4
+};
+struct progress_bar {
+	enum progress_bar_state state;
+	int			progress;
+};
+
 /* Virtual screen. */
 struct screen_sel;
 struct screen_titles;
@@ -988,6 +1002,7 @@ struct screen {
 	struct screen_write_cline	*write_list;
 
 	struct hyperlinks		*hyperlinks;
+	struct progress_bar		 progress_bar;
 };
 
 /* Screen write context. */
@@ -3282,6 +3297,7 @@ int	 screen_set_title(struct screen *, const char *);
 void	 screen_set_path(struct screen *, const char *);
 void	 screen_push_title(struct screen *);
 void	 screen_pop_title(struct screen *);
+void	 screen_set_progress_bar(struct screen *, enum progress_bar_state, int);
 void	 screen_resize(struct screen *, u_int, u_int, int);
 void	 screen_resize_cursor(struct screen *, u_int, u_int, int, int, int);
 void	 screen_set_selection(struct screen *, u_int, u_int, u_int, u_int,
diff --git a/tty-keys.c b/tty-keys.c
index 8fc51174..05ec63c8 100644
--- a/tty-keys.c
+++ b/tty-keys.c
@@ -1383,7 +1383,7 @@ tty_keys_clipboard(struct tty *tty, const char *buf, size_t len, size_t *size)
 	copy[end] = '\0';
 
 	/* Convert from base64. */
-	needed = (end / 4) * 3;
+	needed = ((end + 3) / 4) * 3;
 	if (needed == 0) {
 		free(copy);
 		return (0);