diff --git a/copyparty/__main__.py b/copyparty/__main__.py
index e0a46e79..43fc9916 100644
--- a/copyparty/__main__.py
+++ b/copyparty/__main__.py
@@ -1870,6 +1870,7 @@ def add_ui(ap, retry: int):
     ap2.add_argument("--ui-filesz", metavar="FMT", type=u, default="1", help="default filesize format; one of these: 0, 1, 2, 2c, 3, 3c, 4, 4c, 5, 5c, fuzzy (see UI)")
     ap2.add_argument("--rcm", metavar="TXT", default="yy", help="rightclick-menu; two yes/no options: 1st y/n is enable-custom-menu, 2nd y/n is enable-double")
     ap2.add_argument("--lang", metavar="LANG", type=u, default="eng", help="language, for example \033[32meng\033[0m / \033[32mnor\033[0m / ...")
+    ap2.add_argument("--glang", action="store_true", help="guess the browser's default language, otherwise fall back to \033[33m--lang\033[0m")
     ap2.add_argument("--theme", metavar="NUM", type=int, default=0, help="default theme to use (0..%d)" % (THEMES - 1,))
     ap2.add_argument("--themes", metavar="NUM", type=int, default=THEMES, help="number of themes installed")
     ap2.add_argument("--au-vol", metavar="0-100", type=int, default=50, choices=range(0, 101), help="default audio/video volume percent")
diff --git a/copyparty/authsrv.py b/copyparty/authsrv.py
index 61cf1da9..dc529d7f 100644
--- a/copyparty/authsrv.py
+++ b/copyparty/authsrv.py
@@ -3268,6 +3268,7 @@ class AuthSrv(object):
                 "frand": bool(vf.get("rand")),
                 "lifetime": vn.js_ls["lifetime"],
                 "u2sort": self.args.u2sort,
+                "glang": self.args.glang
             }
             zs = "ui_noacci ui_nocpla ui_noctxb ui_nolbar ui_nombar ui_nonav ui_notree ui_norepl ui_nosrvi"
             for zs in zs.split():
diff --git a/copyparty/web/browser.js b/copyparty/web/browser.js
index 72878b20..277e5f26 100644
--- a/copyparty/web/browser.js
+++ b/copyparty/web/browser.js
@@ -8496,6 +8496,43 @@ var setfszf = (function () {
 	}
 
 	freshen();
+
+	let lmap = [
+		["eng", /^en(-.+)?$/],
+		["nor", /^(no|nb)$/],
+		["chi", /^zh(-.+)?$/],
+		["cze", /^cs$/],
+		["deu", /^de(-.+)?$/],
+		["epo", /^eo$/],
+		["fin", /^fi$/],
+		["fra", /^fr(-.+)?$/],
+		["grc", /^el$/],
+		["hu", /^hu$/],
+		["ita", /^it(-ch)?$/],
+		["jpn", /^ja$/],
+		["kor", /^ko(-.+)?$/],
+		["nl", /^nl(-be)?$/],
+		["nyn", /^nn$/],
+		["pol", /^pl$/],
+		["por", /^pt(-.+)?$/],
+		["rus", /^ru(-md)?$/],
+		["spa", /^es(-.+)?$/],
+		["swe", /^sv(-.+)?$/],
+		["tur", /^tr$/],
+		["ukr", /^uk$/],
+		["vie", /^vi$/]
+	];
+	
+	if (glang && navigator.languages && !/(^|; )cplng=/.test(document.cookie)) {
+		for (let i = 0; i < navigator.languages.length; i++) {
+			for (let j = 0; j < lmap.length; j++) {
+				console.log(lmap[j]);
+				if (lmap[j][1].test(navigator.languages[i])) {
+					return setck('cplng=' + lmap[j][0], location.reload.bind(location));
+				}
+			}
+		}
+	}
 })();