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..af25c7e9 100644
--- a/copyparty/authsrv.py
+++ b/copyparty/authsrv.py
@@ -3273,7 +3273,7 @@ class AuthSrv(object):
             for zs in zs.split():
                 if vf.get(zs):
                     js_htm[zs] = 1
-            zs = "notooltips"
+            zs = "glang notooltips"
             for zs in zs.split():
                 if getattr(self.args, zs, False):
                     js_htm[zs] = 1
diff --git a/copyparty/web/browser.js b/copyparty/web/browser.js
index 3f8255b9..85d03ab5 100644
--- a/copyparty/web/browser.js
+++ b/copyparty/web/browser.js
@@ -713,6 +713,54 @@ var L = Ls[lang] || Ls.eng, LANGS = [];
 for (var a = 0; a < LANGN.length; a++)
 	LANGS.push(LANGN[a][0]);
 
+if (window.glang && navigator.languages && !/\bcplng=/.test(document.cookie))
+	(function() {
+		var lmap = [
+			["eng", /^en/i],
+			["nor", /^n[ob]/i],
+			["chi", /^zh-cn/i],
+			["cze", /^cs/i],
+			["deu", /^de/i],
+			["epo", /^eo/i],
+			["fin", /^fi/i],
+			["fra", /^fr/i],
+			["grc", /^el/i],
+			["hun", /^hu/i],
+			["ita", /^it/i],
+			["jpn", /^ja/i],
+			["kor", /^ko/i],
+			["nld", /^nl/i],
+			["nno", /^nn/i],
+			["pol", /^pl/i],
+			["por", /^pt/i],
+			["rus", /^ru/i],
+			["spa", /^es/i],
+			["swe", /^sv/i],
+			["tur", /^tr/i],
+			["ukr", /^uk/i],
+			["vie", /^vi/i],
+		];
+		for (var a = 0; a < navigator.languages.length; a++) {
+			for (var b = 0; b < lmap.length; b++) {
+				var n = lmap[b][0];
+				if (!lmap[b][1].test(navigator.languages[a]) || !has(LANGS, n))
+					continue;
+
+				if (Ls[n]) {
+					lang = n;
+					L = Ls[n];
+					return;
+				}
+				if (window.stop)
+					window.stop();
+				document.body.innerHTML = 'Loading ' + n;
+				setck("cplng=" + n, location.reload.bind(location));
+				crashed = true;
+				throw 1;
+			}
+		}
+	})();
+
 
 function langtest() {
 	var n = LANGS.length - 1;