diff --git a/format.c b/format.c
index aff72b7c..f5e9d8fd 100644
--- a/format.c
+++ b/format.c
@@ -2320,6 +2320,13 @@ format_cb_version(__unused struct format_tree *ft)
 	return (xstrdup(getversion()));
 }
 
+/* Callback for sixel_support. */
+static void *
+format_cb_sixel_support(__unused struct format_tree *ft)
+{
+	return (xstrdup("0"));
+}
+
 /* Callback for active_window_index. */
 static void *
 format_cb_active_window_index(struct format_tree *ft)
@@ -3147,6 +3154,9 @@ static const struct format_table_entry format_table[] = {
 	{ "session_windows", FORMAT_TABLE_STRING,
 	  format_cb_session_windows
 	},
+	{ "sixel_support", FORMAT_TABLE_STRING,
+	  format_cb_sixel_support
+	},
 	{ "socket_path", FORMAT_TABLE_STRING,
 	  format_cb_socket_path
 	},
diff --git a/tmux.1 b/tmux.1
index 10c9b052..c083ed58 100644
--- a/tmux.1
+++ b/tmux.1
@@ -5956,6 +5956,7 @@ The following variables are available, where appropriate:
 .It Li "session_stack" Ta "" Ta "Window indexes in most recent order"
 .It Li "session_windows" Ta "" Ta "Number of windows in session"
 .It Li "socket_path" Ta "" Ta "Server socket path"
+.It Li "sixel_support" Ta "" Ta "1 if server has support for SIXEL"
 .It Li "start_time" Ta "" Ta "Server start time"
 .It Li "uid" Ta "" Ta "Server UID"
 .It Li "user" Ta "" Ta "Server user"