diff --git a/.changeset/moody-crabs-stare.md b/.changeset/moody-crabs-stare.md
new file mode 100644
index 000000000..19b9a23f2
--- /dev/null
+++ b/.changeset/moody-crabs-stare.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Ensure import.meta.env.SSR is true in SSR mode
diff --git a/packages/astro/src/core/build/static-build.ts b/packages/astro/src/core/build/static-build.ts
index 25e0b04e4..c912b74c1 100644
--- a/packages/astro/src/core/build/static-build.ts
+++ b/packages/astro/src/core/build/static-build.ts
@@ -122,6 +122,7 @@ async function ssrBuild(opts: StaticBuildOptions, internals: BuildInternals, inp
entryFileNames: opts.buildConfig.serverEntry,
},
},
+
ssr: true,
// must match an esbuild target
target: 'esnext',
diff --git a/packages/astro/src/vite-plugin-env/index.ts b/packages/astro/src/vite-plugin-env/index.ts
index d3a5f2635..565ea0dae 100644
--- a/packages/astro/src/vite-plugin-env/index.ts
+++ b/packages/astro/src/vite-plugin-env/index.ts
@@ -78,6 +78,7 @@ export default function envVitePlugin({
privateEnv = getPrivateEnv(config, astroConfig);
if (privateEnv) {
privateEnv.SITE = astroConfig.site ? `'${astroConfig.site}'` : 'undefined';
+ privateEnv.SSR = JSON.stringify(true);
const entries = Object.entries(privateEnv).map(([key, value]) => [
`import.meta.env.${key}`,
value,
@@ -86,6 +87,7 @@ export default function envVitePlugin({
// These additional replacements are needed to match Vite
replacements = Object.assign(replacements, {
'import.meta.env.SITE': astroConfig.site ? `'${astroConfig.site}'` : 'undefined',
+ 'import.meta.env.SSR': JSON.stringify(true),
// This catches destructed `import.meta.env` calls,
// BUT we only want to inject private keys referenced in the file.
// We overwrite this value on a per-file basis.
diff --git a/packages/astro/test/fixtures/ssr-env/astro.config.mjs b/packages/astro/test/fixtures/ssr-env/astro.config.mjs
new file mode 100644
index 000000000..42f10a572
--- /dev/null
+++ b/packages/astro/test/fixtures/ssr-env/astro.config.mjs
@@ -0,0 +1,5 @@
+import preact from '@astrojs/preact';
+
+export default {
+ integrations: [preact()]
+}
diff --git a/packages/astro/test/fixtures/ssr-env/package.json b/packages/astro/test/fixtures/ssr-env/package.json
new file mode 100644
index 000000000..f2d339704
--- /dev/null
+++ b/packages/astro/test/fixtures/ssr-env/package.json
@@ -0,0 +1,9 @@
+{
+ "name": "@test/ssr-env",
+ "version": "0.0.0",
+ "private": true,
+ "dependencies": {
+ "astro": "workspace:*",
+ "@astrojs/preact": "workspace:*"
+ }
+}
diff --git a/packages/astro/test/fixtures/ssr-env/src/components/Env.jsx b/packages/astro/test/fixtures/ssr-env/src/components/Env.jsx
new file mode 100644
index 000000000..776cf3785
--- /dev/null
+++ b/packages/astro/test/fixtures/ssr-env/src/components/Env.jsx
@@ -0,0 +1,7 @@
+
+export default function() {
+ const ssr = import.meta.env.SSR;
+ return (
+ {'' + ssr }
+ )
+}
diff --git a/packages/astro/test/fixtures/ssr-env/src/pages/ssr.astro b/packages/astro/test/fixtures/ssr-env/src/pages/ssr.astro
new file mode 100644
index 000000000..e554d28ea
--- /dev/null
+++ b/packages/astro/test/fixtures/ssr-env/src/pages/ssr.astro
@@ -0,0 +1,9 @@
+---
+import Env from '../components/Env.jsx';
+---
+
+Test
+
+
+
+
diff --git a/packages/astro/test/ssr-env.test.js b/packages/astro/test/ssr-env.test.js
new file mode 100644
index 000000000..da823fa20
--- /dev/null
+++ b/packages/astro/test/ssr-env.test.js
@@ -0,0 +1,29 @@
+import { expect } from 'chai';
+import * as cheerio from 'cheerio';
+import { loadFixture } from './test-utils.js';
+import testAdapter from './test-adapter.js';
+
+describe('SSR Environment Variables', () => {
+ /** @type {import('./test-utils').Fixture} */
+ let fixture;
+
+ before(async () => {
+ fixture = await loadFixture({
+ root: './fixtures/ssr-env/',
+ experimental: {
+ ssr: true,
+ },
+ adapter: testAdapter(),
+ });
+ await fixture.build();
+ });
+
+ it('import.meta.env.SSR is true', async () => {
+ const app = await fixture.loadTestAdapterApp();
+ const request = new Request('http://example.com/ssr');
+ const response = await app.render(request);
+ const html = await response.text();
+ const $ = cheerio.load(html);
+ expect($('#ssr').text()).to.equal('true');
+ });
+});
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 8c22fd695..7be62432c 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -1653,6 +1653,14 @@ importers:
'@astrojs/solid-js': link:../../../../integrations/solid
astro: link:../../..
+ packages/astro/test/fixtures/ssr-env:
+ specifiers:
+ '@astrojs/preact': workspace:*
+ astro: workspace:*
+ dependencies:
+ '@astrojs/preact': link:../../../../integrations/preact
+ astro: link:../../..
+
packages/astro/test/fixtures/ssr-markdown:
specifiers:
astro: workspace:*