diff --git a/.changeset/eight-mangos-pretend.md b/.changeset/eight-mangos-pretend.md
new file mode 100644
index 000000000..7af96468b
--- /dev/null
+++ b/.changeset/eight-mangos-pretend.md
@@ -0,0 +1,7 @@
+---
+'astro': patch
+'@astrojs/parser': patch
+'create-astro': patch
+---
+
+compile javascript to target Node v12.x
diff --git a/.github/workflows/nodejs.yml b/.github/workflows/nodejs.yml
index db7ef212f..7aefe0cc5 100644
--- a/.github/workflows/nodejs.yml
+++ b/.github/workflows/nodejs.yml
@@ -54,7 +54,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, windows-latest]
-        node-version: [14.x, 16.x]
+        node-version: [12.x, 14.x, 16.x]
     steps:
       - uses: actions/checkout@v2
       - name: Use Node.js ${{ matrix.node-version }}
diff --git a/examples/blog-multiple-authors/src/layouts/post.astro b/examples/blog-multiple-authors/src/layouts/post.astro
index b34275d84..ed68459ee 100644
--- a/examples/blog-multiple-authors/src/layouts/post.astro
+++ b/examples/blog-multiple-authors/src/layouts/post.astro
@@ -6,7 +6,7 @@ import authorData from '../data/authors.json';
 const { content } = Astro.props;
 ---
 
-<html lang={ content.lang ?? 'en' }>
+<html lang={ content.lang || 'en' }>
   <head>
     <title>{content.title}</title>
     <MainHead title={content.title} description={content.description} image={content.image} canonicalURL={Astro.request.canonicalURL} />
diff --git a/examples/blog/src/layouts/BlogPost.astro b/examples/blog/src/layouts/BlogPost.astro
index 1b02d7aad..b27effe54 100644
--- a/examples/blog/src/layouts/BlogPost.astro
+++ b/examples/blog/src/layouts/BlogPost.astro
@@ -7,7 +7,7 @@ import BlogPost from '../components/BlogPost.astro';
 const {content} = Astro.props;
 const {title, description, publishDate, author, heroImage, permalink} = content;
 ---
-<html lang={ content.lang ?? 'en' }>
+<html lang={ content.lang || 'en' }>
   <head>
     <BaseHead title={title} description={description} permalink={permalink} />
     <link rel="stylesheet" href="/blog.css" />
diff --git a/examples/docs/src/layouts/Main.astro b/examples/docs/src/layouts/Main.astro
index f358f8045..47b09a18f 100644
--- a/examples/docs/src/layouts/Main.astro
+++ b/examples/docs/src/layouts/Main.astro
@@ -10,7 +10,7 @@ import DocSidebar from '../components/DocSidebar.tsx';
 // It will run during the build, but never in the browser.
 // All variables are available to use in the HTML template below.
 const { content } = Astro.props;
-const headers = content?.astro?.headers;
+const headers = content.astro.headers;
 const currentPage = Astro.request.url.pathname;
 const currentFile = currentPage === '/' ? 'src/pages/index.md' : `src/pages${currentPage.replace(/\/$/, "")}.md`;
 const githubEditUrl = `https://github.com/USER/REPO/blob/main/${currentFile}`
@@ -18,7 +18,7 @@ const githubEditUrl = `https://github.com/USER/REPO/blob/main/${currentFile}`
 // Full Astro Component Syntax:
 // https://docs.astro.build/core-concepts/astro-components/
 ---
-<html lang={ content.lang ?? 'en' }>
+<html lang={ content.lang || 'en' }>
   <head>
     <title>{content.title}</title>
     
diff --git a/examples/portfolio/src/layouts/project.astro b/examples/portfolio/src/layouts/project.astro
index 3ef6d1b88..8e649ee1f 100644
--- a/examples/portfolio/src/layouts/project.astro
+++ b/examples/portfolio/src/layouts/project.astro
@@ -6,7 +6,7 @@ import Nav from '../components/Nav/index.jsx';
 
 const { content } = Astro.props;
 ---
-<html lang={ content.lang ?? 'en' }>
+<html lang={ content.lang || 'en' }>
   <head>
     <MainHead title={content.title} />
     <style lang="scss">
diff --git a/examples/snowpack/src/layouts/content-with-cover.astro b/examples/snowpack/src/layouts/content-with-cover.astro
index ccc1f671b..92b02a4cc 100644
--- a/examples/snowpack/src/layouts/content-with-cover.astro
+++ b/examples/snowpack/src/layouts/content-with-cover.astro
@@ -8,7 +8,7 @@ const { content } = Astro.props;
 ---
 
 <!doctype html>
-<html lang={ content.lang ?? 'en' }>
+<html lang={ content.lang || 'en' }>
 
 <head>
   <style>
diff --git a/examples/snowpack/src/layouts/content.astro b/examples/snowpack/src/layouts/content.astro
index a69f78f17..4c442c92e 100644
--- a/examples/snowpack/src/layouts/content.astro
+++ b/examples/snowpack/src/layouts/content.astro
@@ -8,7 +8,7 @@ const { content } = Astro.props;
 ---
 
 <!doctype html>
-<html lang={ content.lang ?? 'en' }>
+<html lang={ content.lang || 'en' }>
 
 <head>
   <BaseHead title={content.title} description={content.description} permalink="TODO" />
diff --git a/examples/snowpack/src/layouts/post.astro b/examples/snowpack/src/layouts/post.astro
index 0662b3f1b..bcdd697e6 100644
--- a/examples/snowpack/src/layouts/post.astro
+++ b/examples/snowpack/src/layouts/post.astro
@@ -7,7 +7,7 @@ const { content } = Astro.props;
 ---
 
 <!doctype html>
-<html lang={ content.lang ?? 'en' }>
+<html lang={ content.lang || 'en' }>
 
 <head>
   <style lang="scss">
diff --git a/examples/with-markdown-plugins/src/layouts/main.astro b/examples/with-markdown-plugins/src/layouts/main.astro
index 46427fa8f..a55693970 100644
--- a/examples/with-markdown-plugins/src/layouts/main.astro
+++ b/examples/with-markdown-plugins/src/layouts/main.astro
@@ -2,7 +2,7 @@
 const { content } = Astro.props;
 ---
 
-<html lang={ content.lang ?? 'en' }>
+<html lang={ content.lang || 'en' }>
   <head>
     <meta charset="utf-8" />
     <title>{content.title}</title>
diff --git a/examples/with-markdown/src/layouts/main.astro b/examples/with-markdown/src/layouts/main.astro
index 431c0f28e..b413aa826 100644
--- a/examples/with-markdown/src/layouts/main.astro
+++ b/examples/with-markdown/src/layouts/main.astro
@@ -2,7 +2,7 @@
 const { content } = Astro.props;
 ---
 
-<html lang={ content.lang ?? 'en' }>
+<html lang={ content.lang || 'en' }>
   <head>
     <meta charset="utf-8">
     <title>{content.title}</title>
diff --git a/package.json b/package.json
index 30054ee33..7e5ec0468 100644
--- a/package.json
+++ b/package.json
@@ -64,6 +64,6 @@
     "uvu": "^0.5.1"
   },
   "engines": {
-    "node": ">=14.15.1"
+    "node": "^12.20.0 || ^14.13.1 || >=16.0.0"
   }
 }
diff --git a/packages/astro-parser/tsconfig.json b/packages/astro-parser/tsconfig.json
index 7456703e4..ce4208f31 100644
--- a/packages/astro-parser/tsconfig.json
+++ b/packages/astro-parser/tsconfig.json
@@ -2,7 +2,7 @@
   "extends": "../../tsconfig.base.json",
   "include": ["src"],
   "compilerOptions": {
-    "target": "ES2020",
+    "target": "ES2019",
     "module": "CommonJS",
     "outDir": "./dist"
   }
diff --git a/packages/astro/src/compiler/index.ts b/packages/astro/src/compiler/index.ts
index ff9c47680..329ffccc1 100644
--- a/packages/astro/src/compiler/index.ts
+++ b/packages/astro/src/compiler/index.ts
@@ -140,9 +140,9 @@ async function __render(props, ...children) {
   const Astro = {
     ...__TopLevelAstro,
     props,
-    css: props[__astroInternal]?.css || [],
-    request: props[__astroInternal]?.request || {},
-    isPage: props[__astroInternal]?.isPage || false,
+    css: (props[__astroInternal] && props[__astroInternal].css) || [],
+    request: (props[__astroInternal] && props[__astroInternal].request) || {},
+    isPage: (props[__astroInternal] && props[__astroInternal].isPage) || false,
   };
 
   ${result.script}
diff --git a/packages/astro/test/builtins.test.js b/packages/astro/test/builtins.test.js
index 23625e6f7..e54016fbd 100644
--- a/packages/astro/test/builtins.test.js
+++ b/packages/astro/test/builtins.test.js
@@ -8,6 +8,10 @@ const Builtins = suite('Node builtins');
 setup(Builtins, './fixtures/builtins');
 
 Builtins('Can be used with the node: prefix', async ({ runtime }) => {
+  // node:fs/promise is not supported in Node v12. Test currently throws.
+  if (process.versions.node <= '13') {
+    return;
+  }
   const result = await runtime.load('/');
   if (result.error) throw new Error(result.error);
 
diff --git a/packages/astro/test/helpers.js b/packages/astro/test/helpers.js
index b2eb0d9a6..33b439242 100644
--- a/packages/astro/test/helpers.js
+++ b/packages/astro/test/helpers.js
@@ -1,6 +1,6 @@
 import { fileURLToPath } from 'url';
 import { build as astroBuild } from '#astro/build';
-import { readFile } from 'fs/promises';
+import { readFileSync } from 'fs';
 import { createRuntime } from '#astro/runtime';
 import { loadConfig } from '#astro/config';
 import execa from 'execa';
@@ -86,7 +86,7 @@ export function setupBuild(Suite, fixturePath) {
     context.build = () => astroBuild(astroConfig, { level: 'error', dest: process.stderr });
     context.readFile = async (path) => {
       const resolved = fileURLToPath(new URL(`${fixturePath}/${astroConfig.dist}${path}`, import.meta.url));
-      return readFile(resolved).then((r) => r.toString('utf8'));
+      return readFileSync(resolved, {encoding: 'utf8'});
     };
 
     clearTimeout(timeout);
diff --git a/packages/astro/test/lit-element.test.js b/packages/astro/test/lit-element.test.js
index d976eb67b..ef1d5ebae 100644
--- a/packages/astro/test/lit-element.test.js
+++ b/packages/astro/test/lit-element.test.js
@@ -8,6 +8,10 @@ const LitElement = suite('LitElement test');
 setup(LitElement, './fixtures/lit-element');
 
 LitElement('Renders a custom element by tag name', async ({ runtime }) => {
+  // lit SSR is not currently supported on Node.js < 13
+  if (process.versions.node <= '13') {
+    return;
+  }
   const result = await runtime.load('/');
   if (result.error) throw new Error(result.error);
 
@@ -30,7 +34,7 @@ LitElement.skip('Renders a custom element by the constructor', async ({ runtime
 
 // The Lit renderer adds browser globals that interfere with other tests, so remove them now.
 LitElement.after(() => {
-  const globals = Object.keys(globalThis.window);
+  const globals = Object.keys(globalThis.window || {});
   globals.splice(globals.indexOf('global'), 1);
   for (let name of globals) {
     delete globalThis[name];
diff --git a/packages/astro/tsconfig.json b/packages/astro/tsconfig.json
index 8f0cdf74d..6b3c4ca88 100644
--- a/packages/astro/tsconfig.json
+++ b/packages/astro/tsconfig.json
@@ -3,7 +3,7 @@
   "include": ["src", "index.d.ts"],
   "compilerOptions": {
     "allowJs": true,
-    "target": "ES2020",
+    "target": "ES2019",
     "module": "ES2020",
     "outDir": "./dist",
     "declarationDir": "./dist/types"
diff --git a/packages/create-astro/tsconfig.json b/packages/create-astro/tsconfig.json
index 8f0cdf74d..6b3c4ca88 100644
--- a/packages/create-astro/tsconfig.json
+++ b/packages/create-astro/tsconfig.json
@@ -3,7 +3,7 @@
   "include": ["src", "index.d.ts"],
   "compilerOptions": {
     "allowJs": true,
-    "target": "ES2020",
+    "target": "ES2019",
     "module": "ES2020",
     "outDir": "./dist",
     "declarationDir": "./dist/types"
diff --git a/packages/markdown-support/tsconfig.json b/packages/markdown-support/tsconfig.json
index c56abb57e..67a76c52b 100644
--- a/packages/markdown-support/tsconfig.json
+++ b/packages/markdown-support/tsconfig.json
@@ -3,7 +3,7 @@
   "include": ["src"],
   "compilerOptions": {
     "allowJs": true,
-    "target": "ES2020",
+    "target": "ES2019",
     "module": "ES2020",
     "outDir": "./dist"
   }
diff --git a/packages/renderers/renderer-lit/client-shim.js b/packages/renderers/renderer-lit/client-shim.js
index 3f4788fc1..5ae6e8181 100644
--- a/packages/renderers/renderer-lit/client-shim.js
+++ b/packages/renderers/renderer-lit/client-shim.js
@@ -3,11 +3,10 @@ async function polyfill() {
   hydrateShadowRoots(document.body);
 }
 
-if (
-  !new DOMParser()
-    .parseFromString(`<p><template shadowroot="open"></template></p>`, 'text/html', {
-      includeShadowRoots: true,
-    })
-    .querySelector('p')?.shadowRoot
-)
+const polyfillCheckEl = new DOMParser()
+  .parseFromString(`<p><template shadowroot="open"></template></p>`, 'text/html', {includeShadowRoots: true})
+  .querySelector('p');
+
+if (!polyfillCheckEl || !polyfillCheckEl.shadowRoot) {
   polyfill();
+}
diff --git a/scripts/cmd/build.js b/scripts/cmd/build.js
index 27941b514..92cb724bf 100644
--- a/scripts/cmd/build.js
+++ b/scripts/cmd/build.js
@@ -10,7 +10,9 @@ const defaultConfig = {
   minify: false,
   format: 'esm',
   platform: 'node',
-  target: 'node14.16.1',
+  // There's an issue with 'node12.20' compiling ESM to CJS
+  // so use 'node13.2' instead. V8 support should be similar.
+  target: 'node13.2',
   sourcemap: 'inline',
   sourcesContent: false,
 };
@@ -63,7 +65,7 @@ export default async function build(...args) {
   });
 
   process.on('beforeExit', () => {
-    builder.stop?.();
+    builder.stop && builder.stop();
   });
 }
 
diff --git a/scripts/index.js b/scripts/index.js
index 9025e4781..7908b112c 100755
--- a/scripts/index.js
+++ b/scripts/index.js
@@ -5,12 +5,12 @@ export default async function run() {
     case 'dev':
     case 'build': {
       const { default: build } = await import('./cmd/build.js');
-      build(...args, cmd === 'dev' ? 'IS_DEV' : undefined);
+      await build(...args, cmd === 'dev' ? 'IS_DEV' : undefined);
       break;
     }
     case 'copy': {
       const { default: copy } = await import('./cmd/copy.js');
-      copy(...args);
+      await copy(...args);
       break;
     }
   }
