--- a/Cargo.lock
+++ b/Cargo.lock
@@ -429,6 +429,12 @@
 checksum = "8f42a60cbdf9a97f5d2305f08a87dc4e09308d1276d28c869c684d7777685682"
 
 [[package]]
+name = "lazy_static"
+version = "1.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "20870f649af7073d53e38067b2a84312175d56ea15217e1b15bc83506ec50afb"
+
+[[package]]
 name = "lewton"
 version = "0.9.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -553,6 +559,21 @@
 ]
 
 [[package]]
+name = "nanoserde"
+version = "0.1.37"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5de9cf844ab1e25a0353525bd74cb889843a6215fa4a0d156fd446f4857a1b99"
+dependencies = [
+ "nanoserde-derive",
+]
+
+[[package]]
+name = "nanoserde-derive"
+version = "0.1.22"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e943b2c21337b7e3ec6678500687cdc741b7639ad457f234693352075c082204"
+
+[[package]]
 name = "ndk-sys"
 version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -654,6 +675,26 @@
 ]
 
 [[package]]
+name = "quad-storage"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e73edba8c792f3b5a45c68a1086f6f8c1bbda34ab9399a7faabd7dc7d4e14a0e"
+dependencies = [
+ "lazy_static",
+ "nanoserde",
+ "quad-storage-sys",
+]
+
+[[package]]
+name = "quad-storage-sys"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1187c77ced2cc6ae79bd6e35cc09e22159164a05c4d867e299bfbf1f801e9157"
+dependencies = [
+ "sapp-jsutils",
+]
+
+[[package]]
 name = "quote"
 version = "1.0.47"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -747,6 +788,12 @@
 ]
 
 [[package]]
+name = "sapp-jsutils"
+version = "0.1.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c6673c9c245fda02a1e826e199133d1c3d1b8e4a392c9dfe55e4f90a2489b149"
+
+[[package]]
 name = "scorch"
 version = "0.4.1"
 dependencies = [
@@ -754,6 +801,7 @@
  "fluent-bundle",
  "macroquad",
  "minisign-verify",
+ "quad-storage",
  "self-replace",
  "serde",
  "serde_json",
--- a/Cargo.toml	2026-11-08 09:53:42.000000000 -0300
+++ b/Cargo.toml	2026-11-08 17:35:50.948834124 -0300
@@ -13,7 +13,6 @@
 self-update = ["dep:minisign-verify", "dep:self-replace", "dep:sha2", "dep:ureq"]
 
 [dependencies]
-dirs = "7.0.0"
 fluent-bundle = "0.16.0"
 macroquad = { version = "0.4.16", features = ["audio"] }
 minisign-verify = { version = "0.3.0", optional = true }
@@ -21,10 +20,18 @@
 serde = { version = "1.0.229", features = ["derive"] }
 serde_json = "1.0.154"
 sha2 = { version = "0.11.1", optional = true }
-sys-locale = "0.3.2"
 unic-langid = "0.9.6"
 ureq = { version = "3.5.0", optional = true }
 
+# Desktop only: the data folder and the OS language have no meaning in a browser.
+[target.'cfg(not(target_arch = "wasm32"))'.dependencies]
+dirs = "7.0.0"
+sys-locale = "0.3.2"
+
+# Browser build (FredyGames): saves go to localStorage.
+[target.'cfg(target_arch = "wasm32")'.dependencies]
+quad-storage = "0.1.3"
+
 # Puts the icon into scorch.exe (build.rs).
 [target.'cfg(windows)'.build-dependencies]
 winresource = "0.1.34"
--- a/src/crash.rs
+++ b/src/crash.rs
@@ -27,6 +27,10 @@
 
 /// Writes a crash report on any panic, then lets the default handler run.
 pub fn install() {
+    // Browser build: no data folder, and SystemTime::now() panics on wasm32-unknown-unknown.
+    if cfg!(target_arch = "wasm32") {
+        return;
+    }
     let default = std::panic::take_hook();
     std::panic::set_hook(Box::new(move |info| {
         // No working sound device: the audio thread gives up and the game carries on silently. Not a crash.
@@ -78,10 +82,16 @@
     )
 }
 
+#[cfg(not(target_arch = "wasm32"))]
 fn dir() -> Option<PathBuf> {
     dirs::data_dir().map(|d| d.join("scorch"))
 }
 
+#[cfg(target_arch = "wasm32")]
+fn dir() -> Option<PathBuf> {
+    None
+}
+
 fn write(text: &str) -> Option<PathBuf> {
     let dir = dir()?;
     fs::create_dir_all(&dir).ok()?;
--- a/src/i18n.rs
+++ b/src/i18n.rs
@@ -57,7 +57,11 @@
 /// The operating system's language, if the game has it, else English. Used
 /// once, on the first run; after that the player's choice is saved.
 pub fn detect() -> Language {
-    match sys_locale::get_locale() {
+    #[cfg(target_arch = "wasm32")]
+    let locale: Option<String> = None;
+    #[cfg(not(target_arch = "wasm32"))]
+    let locale = sys_locale::get_locale();
+    match locale {
         Some(l) if l.to_lowercase().starts_with("uk") => Language::Ukrainian,
         _ => Language::English,
     }
--- a/src/main.rs
+++ b/src/main.rs
@@ -412,7 +412,7 @@
                     }
                     Some(PauseAction::SaveAndQuit) => {
                         self.save_battle(&battle);
-                        Screen::Exit
+                        exit_screen()
                     }
                     Some(PauseAction::BattleLog) => {
                         self.log_open = true;
@@ -534,7 +534,7 @@
             }
         } else if item("menu-about") {
             Screen::About
-        } else if item("menu-quit") {
+        } else if !cfg!(target_arch = "wasm32") && item("menu-quit") {
             Screen::Exit
         } else {
             Screen::Menu
@@ -1012,6 +1012,15 @@
     }
 }
 
+/// What "quit" does: leave the loop on desktop; in the browser there is no window to close, so go back to the menu.
+fn exit_screen() -> Screen {
+    if cfg!(target_arch = "wasm32") {
+        Screen::Menu
+    } else {
+        Screen::Exit
+    }
+}
+
 /// `--crash-test`: a deliberate panic, to try the crash report.
 fn crash_test() -> ! {
     panic!("crash test requested with --crash-test");
--- a/src/save.rs
+++ b/src/save.rs
@@ -5,8 +5,6 @@
 //!     Rewritten at the start of every turn, deleted when the game ends.
 //!   - `profile.json`: settings and all-time stats.
 
-use std::fs;
-use std::path::PathBuf;
 use std::sync::atomic::{AtomicBool, Ordering};
 
 /// Set by `--screen` (a developer aid): nothing is written or deleted.
@@ -86,7 +84,7 @@
 }
 
 pub fn run_exists() -> bool {
-    path(RUN).is_some_and(|p| p.exists())
+    backend::exists(RUN)
 }
 
 pub fn store_run(run: &RunOut<'_>) {
@@ -101,9 +99,7 @@
     if READ_ONLY.load(Ordering::Relaxed) {
         return;
     }
-    if let Some(p) = path(RUN) {
-        let _ = fs::remove_file(p);
-    }
+    backend::remove(RUN);
 }
 
 pub fn store_profile(profile: &Profile) {
@@ -116,12 +112,73 @@
     profile
 }
 
-fn path(name: &str) -> Option<PathBuf> {
-    dirs::data_dir().map(|d| d.join("scorch").join(name))
+/// Where the files live. Desktop: the platform data folder. Browser build (FredyGames): localStorage, under keys
+/// prefixed with "scorch.".
+#[cfg(not(target_arch = "wasm32"))]
+mod backend {
+    use std::fs;
+    use std::path::PathBuf;
+
+    fn path(name: &str) -> Option<PathBuf> {
+        dirs::data_dir().map(|d| d.join("scorch").join(name))
+    }
+
+    pub fn exists(name: &str) -> bool {
+        path(name).is_some_and(|p| p.exists())
+    }
+
+    pub fn remove(name: &str) {
+        if let Some(p) = path(name) {
+            let _ = fs::remove_file(p);
+        }
+    }
+
+    pub fn read(name: &str) -> Option<String> {
+        fs::read_to_string(path(name)?).ok()
+    }
+
+    /// Writes to a temporary file first, then renames it over the old one,
+    /// so a crash mid-write never leaves a half-written save.
+    pub fn write(name: &str, text: &str) -> Result<(), String> {
+        let path = path(name).ok_or("no data folder")?;
+        (|| -> std::io::Result<()> {
+            if let Some(dir) = path.parent() {
+                fs::create_dir_all(dir)?;
+            }
+            let tmp = path.with_extension("tmp");
+            fs::write(&tmp, text)?;
+            fs::rename(tmp, &path)
+        })()
+        .map_err(|e| e.to_string())
+    }
+}
+
+#[cfg(target_arch = "wasm32")]
+mod backend {
+    fn key(name: &str) -> String {
+        format!("scorch.{name}")
+    }
+
+    pub fn exists(name: &str) -> bool {
+        read(name).is_some()
+    }
+
+    pub fn remove(name: &str) {
+        quad_storage::STORAGE.lock().unwrap().remove(&key(name));
+    }
+
+    pub fn read(name: &str) -> Option<String> {
+        quad_storage::STORAGE.lock().unwrap().get(&key(name))
+    }
+
+    pub fn write(name: &str, text: &str) -> Result<(), String> {
+        quad_storage::STORAGE.lock().unwrap().set(&key(name), text);
+        Ok(())
+    }
 }
 
 fn load<T: DeserializeOwned>(name: &str) -> Option<T> {
-    let text = fs::read_to_string(path(name)?).ok()?;
+    let text = backend::read(name)?;
     match serde_json::from_str(&text) {
         Ok(value) => Some(value),
         Err(e) => {
@@ -131,23 +188,13 @@
     }
 }
 
-/// Writes to a temporary file first, then renames it over the old one,
-/// so a crash mid-write never leaves a half-written save.
 fn store<T: Serialize>(name: &str, value: &T) {
-    let Some(path) = path(name) else {
-        return;
-    };
     if READ_ONLY.load(Ordering::Relaxed) {
         return;
     }
-    let result = (|| -> std::io::Result<()> {
-        if let Some(dir) = path.parent() {
-            fs::create_dir_all(dir)?;
-        }
-        let tmp = path.with_extension("tmp");
-        fs::write(&tmp, serde_json::to_string(value)?)?;
-        fs::rename(tmp, &path)
-    })();
+    let result = serde_json::to_string(value)
+        .map_err(|e| e.to_string())
+        .and_then(|text| backend::write(name, &text));
     if let Err(e) = result {
         eprintln!("Could not save {name}: {e}");
     }