diff --git a/crates/ui-egui/Cargo.toml b/crates/ui-egui/Cargo.toml
index aa9fe54f66..42e9474f07 100644
--- a/crates/ui-egui/Cargo.toml
+++ b/crates/ui-egui/Cargo.toml
@@ -71,7 +71,7 @@ rfd = { workspace = true, features = ["file-handle-inner"] }
 wasm-bindgen-futures = "0.4"
 wasm-bindgen = "0.2"
 js-sys = "0.3"
-web-sys = { version = "0.3", features = ["Window", "Document", "Element", "HtmlElement", "HtmlAnchorElement", "Blob", "BlobPropertyBag", "Url", "HtmlIFrameElement", "HtmlImageElement", "HtmlCollection", "Node", "EventTarget"] }
+web-sys = { version = "0.3", features = ["Window", "Document", "Element", "HtmlElement", "HtmlAnchorElement", "Blob", "BlobPropertyBag", "Url", "HtmlIFrameElement", "HtmlImageElement", "HtmlCollection", "Node", "EventTarget", "Navigator"] }
 
 [dev-dependencies]
 pdfcraft-xfa = { workspace = true }
diff --git a/crates/ui-egui/src/i18n/mod.rs b/crates/ui-egui/src/i18n/mod.rs
index 0d097f6cd3..20c0fd0467 100644
--- a/crates/ui-egui/src/i18n/mod.rs
+++ b/crates/ui-egui/src/i18n/mod.rs
@@ -390,9 +390,23 @@ fn first_supported(list: &str) -> Option<Lang> {
     list.split(['(', ')', ',', '"', '\n']).map(str::trim).filter(|s| !s.is_empty()).find_map(lang_from_tag)
 }
 
+/// The first supported language among BCP 47 tags in preference order, as the browser lists them
+/// in `navigator.languages` (#2954). Only the first few tags are looked at: the list is short in
+/// practice, and a page can't make Auto walk an unbounded one.
+#[cfg_attr(not(target_arch = "wasm32"), allow(dead_code))]
+fn first_supported_tag<S: AsRef<str>>(tags: impl IntoIterator<Item = S>) -> Option<Lang> {
+    tags.into_iter().take(32).find_map(|tag| lang_from_tag(tag.as_ref().trim()))
+}
+
+/// The browser's preferred languages, as the desktop builds use the system's: `navigator.languages`
+/// in order, then `navigator.language` (kept within the 32 tags `first_supported_tag` reads).
+/// English when the browser offers none we have a catalog for.
 #[cfg(target_arch = "wasm32")]
 fn detect_system_lang() -> Lang {
-    Lang::EN
+    let Some(navigator) = web_sys::window().map(|w| w.navigator()) else { return Lang::EN };
+    let mut tags: Vec<String> = navigator.languages().iter().take(31).filter_map(|v| v.as_string()).collect();
+    tags.extend(navigator.language());
+    first_supported_tag(&tags).unwrap_or(Lang::EN)
 }
 
 thread_local! {
@@ -650,6 +664,21 @@ mod tests {
         assert_eq!(first_supported("("), None);
     }
 
+    /// #2954: the web build's Auto language follows the browser's preferred languages in order,
+    /// skipping ones without a catalog, and is English only when none is supported.
+    #[test]
+    fn browser_language_list_is_followed_in_order() {
+        assert_eq!(first_supported_tag(["it-IT", "en-US"]), Lang::from_code("it"));
+        assert_eq!(first_supported_tag(["xx-YY", "ja", "fr-FR"]), Some(JA()));
+        assert_eq!(first_supported_tag(["zh-TW"]), Lang::from_code("zh-hant"));
+        assert_eq!(first_supported_tag(["en-GB", "fr-FR"]), Some(Lang::EN));
+        assert_eq!(first_supported_tag([" pt-PT "]), Lang::from_code("pt-br"));
+        assert_eq!(first_supported_tag(["", "xx"]), None);
+        assert_eq!(first_supported_tag(Vec::<String>::new()), None);
+        let long = std::iter::repeat_n("xx", 10_000).chain(["fr"]);
+        assert_eq!(first_supported_tag(long), None, "only the first tags are read");
+    }
+
     #[test]
     fn windows_display_language_resolves_chinese_scripts() {
         for tag in ["zh-CN", "zh-SG", "zh-Hans", "zh-Hans-CN"] {