diff --git a/.github/workflows/release_nightly.yml b/.github/workflows/release_nightly.yml
index df3fbba9ef9c..07547e351fdc 100644
--- a/.github/workflows/release_nightly.yml
+++ b/.github/workflows/release_nightly.yml
@@ -336,6 +336,7 @@ jobs:
         with:
           toolchain: 1.81.0
           targets: wasm32-unknown-unknown
+          components: rust-src
 
       - name: Setup Node.js
         uses: actions/setup-node@v4
diff --git a/.github/workflows/test_extension_dockerfile.yml b/.github/workflows/test_extension_dockerfile.yml
index 27acaa7c89e7..f15d5ee104f7 100644
--- a/.github/workflows/test_extension_dockerfile.yml
+++ b/.github/workflows/test_extension_dockerfile.yml
@@ -21,6 +21,7 @@ jobs:
         with:
           toolchain: stable
           targets: wasm32-unknown-unknown
+          components: rust-src
 
       - name: Setup Node.js
         uses: actions/setup-node@v4
diff --git a/web/README.md b/web/README.md
index fef30a31af9f..9b54f123641c 100644
--- a/web/README.md
+++ b/web/README.md
@@ -103,9 +103,10 @@ In this project, you may run the following commands to build all packages:
     -   This will build the wasm binary and every node package (notably selfhosted and extension).
     -   Output will be available in the `dist/` folder of each package (for example, `./packages/selfhosted/dist`).
     -   You may also use `npm run build:debug` to disable Webpack optimizations and activate the (extremely verbose) ActionScript debugging output.
-    -   There is `npm run build:dual-wasm` as well, to build a second WebAssembly module that makes use of some WebAssembly extensions,
-        potentially resulting in better performance in browsers that support them, at the expense of longer build time.
+    -   There is `npm run build:dual-wasm` as well, to build a second WebAssembly module that disables all supported WebAssembly extensions,
+        potentially resulting in support for more browsers, at the expense of longer build time.
     -   `npm run build:repro` enables reproducible builds. Note that this also requires a `version_seal.json`, which is not provided in the normal Git repository - only specially-marked reproducible source archives. Running this without a version seal will generate one based on the current state of your environment.
+    -   You will also need to run `rustup component add rust-src` with either of the previous two commands since we rebuild std for the vanilla WASM module.
 
 From here, you may follow the instructions to [use Ruffle on your website](packages/selfhosted/README.md),
 run a demo locally with `npm run demo`, or [install the extension in your browser](https://github.com/ruffle-rs/ruffle/wiki/Using-Ruffle#browser-extension).
diff --git a/web/docker/Dockerfile b/web/docker/Dockerfile
index 1f2797972708..eafcaa30b193 100644
--- a/web/docker/Dockerfile
+++ b/web/docker/Dockerfile
@@ -11,7 +11,7 @@ RUN wget --progress=:giga https://github.com/WebAssembly/binaryen/releases/downl
     mv wasm-opt /usr/local/bin
 
 # Installing Rust using rustup:
-RUN wget 'https://sh.rustup.rs' --quiet -O- | sh -s -- -y --profile minimal --target wasm32-unknown-unknown
+RUN wget 'https://sh.rustup.rs' --quiet -O- | sh -s -- -y --profile minimal --target wasm32-unknown-unknown --component rust-src
 ENV PATH="/root/.cargo/bin:$PATH"
 # wasm-bindgen-cli version must match wasm-bindgen crate version.
 # Be sure to update in test_web.yml, release_nightly.yml, Cargo.toml, and web/README.md as well.
diff --git a/web/package.json b/web/package.json
index 8f85844447d4..989c0a35c3c5 100644
--- a/web/package.json
+++ b/web/package.json
@@ -45,8 +45,8 @@
     "scripts": {
         "build": "npm run build --workspace=ruffle-core && npm run build --workspace=ruffle-demo --workspace=ruffle-extension --workspace=ruffle-selfhosted",
         "build:debug": "cross-env NODE_ENV=development CARGO_FEATURES=avm_debug npm run build",
-        "build:dual-wasm": "cross-env ENABLE_WASM_EXTENSIONS=true npm run build",
-        "build:repro": "cross-env ENABLE_WASM_EXTENSIONS=true ENABLE_VERSION_SEAL=true npm run build",
+        "build:dual-wasm": "cross-env BUILD_WASM_MVP=true npm run build",
+        "build:repro": "cross-env BUILD_WASM_MVP=true ENABLE_VERSION_SEAL=true npm run build",
         "demo": "npm run preview --workspace ruffle-demo",
         "test": "npm test --workspaces --if-present",
         "wdio": "npm run wdio --workspaces --if-present --",
diff --git a/web/packages/core/tools/build_wasm.ts b/web/packages/core/tools/build_wasm.ts
index 61c93ea52c3a..bab1d3a41b28 100644
--- a/web/packages/core/tools/build_wasm.ts
+++ b/web/packages/core/tools/build_wasm.ts
@@ -42,12 +42,19 @@ function cargoBuild({
     profile,
     features,
     rustFlags,
+    extensions,
 }: {
     profile?: string;
     features?: string[];
     rustFlags?: string[];
+    extensions?: boolean;
 }) {
     let args = ["build", "--locked", "--target", "wasm32-unknown-unknown"];
+    if (!extensions) {
+        args.push("-Z");
+        args.push("build-std=std,panic_abort");
+    }
+
     if (profile) {
         args.push("--profile", profile);
     }
@@ -73,6 +80,7 @@ function cargoBuild({
     execFileSync("cargo", args, {
         env: Object.assign(Object.assign({}, process.env), {
             RUSTFLAGS: totalRustFlags,
+            RUSTC_BOOTSTRAP: extensions ? "0" : "1",
         }),
         stdio: "inherit",
     });
@@ -95,6 +103,8 @@ function buildWasm(
         );
         wasmBindgenFlags.push("--reference-types");
         wasmOptFlags.push("--enable-reference-types");
+    } else {
+        rustFlags.push("-C", "target-cpu=mvp");
     }
     let originalWasmPath;
     if (wasmSource === "cargo" || wasmSource === "cargo_and_store") {
@@ -102,6 +112,7 @@ function buildWasm(
         cargoBuild({
             profile,
             rustFlags,
+            extensions,
         });
         originalWasmPath = `../../../target/wasm32-unknown-unknown/${profile}/ruffle_web.wasm`;
         if (wasmSource === "cargo_and_store") {
@@ -144,7 +155,7 @@ function detectWasmOpt() {
         return false;
     }
 }
-const buildExtensions = !!process.env["ENABLE_WASM_EXTENSIONS"];
+const buildWasmMvp = !!process.env["BUILD_WASM_MVP"];
 const wasmSource = process.env["WASM_SOURCE"] || "cargo";
 const hasWasmOpt = detectWasmOpt();
 if (!hasWasmOpt) {
@@ -156,15 +167,15 @@ if (wasmSource === "cargo_and_store") {
     rmSync("../../dist", { recursive: true, force: true });
     mkdirSync("../../dist");
 }
-buildWasm("web-vanilla-wasm", "ruffle_web", hasWasmOpt, false, wasmSource);
-if (buildExtensions) {
-    buildWasm(
-        "web-wasm-extensions",
-        "ruffle_web-wasm_extensions",
-        hasWasmOpt,
-        true,
-        wasmSource,
-    );
+buildWasm(
+    "web-wasm-extensions",
+    "ruffle_web-wasm_extensions",
+    hasWasmOpt,
+    true,
+    wasmSource,
+);
+if (buildWasmMvp) {
+    buildWasm("web-vanilla-wasm", "ruffle_web", hasWasmOpt, false, wasmSource);
 } else {
-    copyStandIn("ruffle_web", "ruffle_web-wasm_extensions");
+    copyStandIn("ruffle_web-wasm_extensions", "ruffle_web");
 }