diff --git a/README.md b/README.md
index 6e6ac6f..86bd708 100644
--- a/README.md
+++ b/README.md
@@ -9,5 +9,5 @@
 
 ### Client
 
-1. Make sure you have the `wasm32-unknown-unknown` target installed, `wasm-bindgen` executable installed, and `bash`, `python3` packages (`python3` is used for `http.server` module)
-2. Run `bash build.sh` to build and start a webserver
+1. Make sure you have the `wasm32-unknown-unknown` target installed, `wasm-bindgen` executable installed (and optionally `wasm-opt`), and `bash`, `python3` packages (`python3` is used for `http.server` module)
+2. Run `bash build.sh` to build without wasm-opt and start a webserver, add any argument to call wasm-opt
diff --git a/client/build.sh b/client/build.sh
index e1b1ff4..8c7ca0e 100755
--- a/client/build.sh
+++ b/client/build.sh
@@ -6,5 +6,9 @@ rm -rf out/ || true
 mkdir out/
 cargo build --target wasm32-unknown-unknown --release
 wasm-bindgen --weak-refs --no-typescript --target no-modules --out-dir out/ ../target/wasm32-unknown-unknown/release/wstcp_client.wasm
+if [[ "$#" > 0 ]]; then
+  mv out/wstcp_client_bg.wasm out/wstcp_client_unoptimized.wasm
+  wasm-opt -O4 out/wstcp_client_unoptimized.wasm -o out/wstcp_client_bg.wasm
+fi
 cp -r src/web/* out/
 (cd out; python3 -m http.server)
diff --git a/client/src/web/index.js b/client/src/web/index.js
index 2380ca9..0468036 100644
--- a/client/src/web/index.js
+++ b/client/src/web/index.js
@@ -4,17 +4,43 @@
         "color:red;font-size:2rem;font-weight:bold"
     );
     await wasm_bindgen("./wstcp_client_bg.wasm");
+
     const tconn0 = performance.now();
     // args: websocket url, user agent, redirect limit 
     let wstcp = await new wasm_bindgen.WsTcp("wss://localhost:4000", navigator.userAgent, 10);
     const tconn1 = performance.now();
     console.warn(`conn establish took ${tconn1 - tconn0} ms or ${(tconn1 - tconn0) / 1000} s`);
-    const t0 = performance.now();
-    let resp = await wstcp.fetch("http://httpbin.org/redirect/11");
-    const t1 = performance.now();
 
-    console.warn(resp);
-    console.warn(Object.fromEntries(resp.headers));
-    console.warn(await resp.text());
-    console.warn(`mux 1 took ${t1 - t0} ms or ${(t1 - t0) / 1000} s`);
+    const test_mux = async (url) => {
+        const t0 = performance.now();
+        await wstcp.fetch(url);
+        const t1 = performance.now();
+        return t1 - t0;
+    };
+
+    const test_native = async (url) => {
+        const t0 = performance.now();
+        await fetch(url);
+        const t1 = performance.now();
+        return t1 - t0;
+    };
+
+    const num_tests = 10;
+
+    let total_mux = 0;
+    for (const _ of Array(num_tests).keys()) {
+        total_mux += await test_mux("https://httpbin.org/get");
+    }
+    total_mux = total_mux / num_tests;
+
+    let total_native = 0;
+    for (const _ of Array(num_tests).keys()) {
+        total_native += await test_native("https://httpbin.org/get");
+    }
+    total_native = total_native / num_tests;
+
+    console.warn(`avg mux (10) took ${total_mux} ms or ${total_mux / 1000} s`);
+    console.warn(`avg native (10) took ${total_native} ms or ${total_native / 1000} s`);
+    console.warn(`mux - native: ${total_mux - total_native} ms or ${(total_mux - total_native) / 1000} s`);
+    alert("you can open console now");
 })();