diff --git a/README.md b/README.md
index b791dc9..8a31c39 100644
--- a/README.md
+++ b/README.md
@@ -63,3 +63,17 @@ SITE=https://example.github.io BASE=/Incognito-Wiki npm run build
 Netlify reads `netlify.toml`, runs `npm run build`, and publishes `dist`. Configure `SITE` and `BASE` as environment values for the selected production hostname and path.
 
 The removable workflow at `.github/workflows/deploy.yml` optionally deploys the GitHub mirror to Pages after a push to `main` or a manual dispatch. Set the public repository variables `SITE_URL` and `BASE_PATH` on GitHub. The workflow is GitHub-specific; Forgejo ignores it, and removing the workflow or `netlify.toml` does not affect local development or verification.
+
+## Matomo analytics
+
+The wiki uses self-hosted Matomo only after a visitor explicitly accepts analytics. The client is loaded from `https://analytics.msvincognito.nl/`, uses site ID `1`, and disables analytics cookies. Visitors can decline without losing functionality and can reopen **Privacy settings** to withdraw consent.
+
+Before deploying analytics changes, the Matomo administrator must verify:
+
+- IP anonymization is enabled;
+- raw logs and analytics reports use documented, proportionate retention periods;
+- administrator access is restricted and reviewed;
+- analytics data is not reused for advertising or cross-site profiling; and
+- the [MSV Incognito privacy policy](https://msvincognito.nl/privacy-policy) accurately states the controller, purpose, data categories, retention, withdrawal process, and data-subject rights.
+
+The frontend consent gate is only one part of GDPR and ePrivacy compliance. Revisit the legal and server configuration when Matomo features or processing purposes change.
diff --git a/astro.config.mjs b/astro.config.mjs
index 9b5d23d..3c70b31 100644
--- a/astro.config.mjs
+++ b/astro.config.mjs
@@ -4,6 +4,10 @@ import { sidebar } from './src/config/sidebar.mjs';
 
 const site = process.env.SITE || 'http://localhost:4321';
 const base = process.env.BASE || '/';
+const normalizedBase = base === '/'
+  ? ''
+  : `/${base.replace(/^\/+|\/+$/g, '')}`;
+const matomoConsentScript = `${normalizedBase}/matomo-consent.js`;
 
 export default defineConfig({
   site,
@@ -22,6 +26,15 @@ export default defineConfig({
       },
       favicon: '/favicon.ico',
       customCss: ['./src/styles/incognito.css'],
+      head: [
+        {
+          tag: 'script',
+          attrs: {
+            src: matomoConsentScript,
+            defer: true,
+          },
+        },
+      ],
       social: [
         {
           icon: 'external',
diff --git a/src/styles/incognito.css b/src/styles/incognito.css
index 2544204..c122d18 100644
--- a/src/styles/incognito.css
+++ b/src/styles/incognito.css
@@ -47,3 +47,88 @@
   background: color-mix(in srgb, var(--incognito-violet) 22%, transparent);
   color: var(--sl-color-gray-1);
 }
+
+#incognito-analytics-consent {
+  position: fixed;
+  z-index: 1000;
+  inset-inline: max(1rem, env(safe-area-inset-left)) max(1rem, env(safe-area-inset-right));
+  inset-block-end: max(1rem, env(safe-area-inset-bottom));
+  display: grid;
+  gap: 1rem;
+  width: min(44rem, calc(100% - 2rem));
+  margin-inline: auto;
+  padding: 1.25rem;
+  color: #fff;
+  background: var(--incognito-navy);
+  border: 1px solid color-mix(in srgb, var(--incognito-bright) 45%, transparent);
+  border-radius: 0.75rem;
+  box-shadow: 0 1rem 3rem rgb(0 0 0 / 30%);
+}
+
+#incognito-analytics-consent[hidden],
+#incognito-privacy-settings[hidden] {
+  display: none;
+}
+
+.incognito-consent-copy h2 {
+  margin: 0 0 0.5rem;
+  color: inherit;
+  font-size: 1.125rem;
+}
+
+.incognito-consent-copy p {
+  margin: 0 0 0.5rem;
+  line-height: 1.55;
+}
+
+.incognito-consent-copy a {
+  color: var(--incognito-light);
+}
+
+.incognito-consent-actions {
+  display: grid;
+  grid-template-columns: repeat(2, minmax(0, 1fr));
+  gap: 0.75rem;
+}
+
+.incognito-consent-action,
+#incognito-privacy-settings {
+  min-height: 2.75rem;
+  border: 2px solid var(--incognito-light);
+  border-radius: 0.5rem;
+  color: var(--incognito-navy);
+  background: var(--incognito-light);
+  font: inherit;
+  font-weight: 700;
+  cursor: pointer;
+}
+
+.incognito-consent-action:focus-visible,
+#incognito-privacy-settings:focus-visible {
+  outline: 3px solid var(--incognito-pink);
+  outline-offset: 3px;
+}
+
+#incognito-privacy-settings {
+  position: fixed;
+  z-index: 999;
+  inset-inline-end: max(1rem, env(safe-area-inset-right));
+  inset-block-end: max(1rem, env(safe-area-inset-bottom));
+  min-height: 2.25rem;
+  padding-inline: 0.75rem;
+  border-width: 1px;
+  font-size: 0.8125rem;
+}
+
+@media (min-width: 50rem) {
+  #incognito-analytics-consent {
+    grid-template-columns: minmax(0, 1fr) 18rem;
+    align-items: end;
+  }
+}
+
+@media (max-width: 30rem) {
+  .incognito-consent-actions {
+    grid-template-columns: 1fr;
+  }
+}
diff --git a/tests/matomo-build.test.mjs b/tests/matomo-build.test.mjs
new file mode 100644
index 0000000..334893b
--- /dev/null
+++ b/tests/matomo-build.test.mjs
@@ -0,0 +1,50 @@
+import assert from 'node:assert/strict';
+import { execFile } from 'node:child_process';
+import { access, mkdtemp, readFile, readdir, rm } from 'node:fs/promises';
+import { join } from 'node:path';
+import { promisify } from 'node:util';
+import test from 'node:test';
+import { parseHTML } from 'linkedom';
+
+const execFileAsync = promisify(execFile);
+
+async function collectCss(directory) {
+  const entries = await readdir(directory, { withFileTypes: true });
+  const chunks = [];
+  for (const entry of entries) {
+    const path = join(directory, entry.name);
+    if (entry.isDirectory()) chunks.push(await collectCss(path));
+    if (entry.isFile() && entry.name.endsWith('.css')) chunks.push(await readFile(path, 'utf8'));
+  }
+  return chunks.join('\n');
+}
+
+test('subpath production build includes the local consent controller and its UI styles', async () => {
+  const output = await mkdtemp(join(process.cwd(), '.matomo-build-'));
+  try {
+    await execFileAsync('node_modules/.bin/astro', ['build', '--outDir', output], {
+      env: {
+        ...process.env,
+        SITE: 'https://example.github.io',
+        BASE: '/Incognito-Wiki',
+      },
+      maxBuffer: 10 * 1024 * 1024,
+    });
+
+    const html = await readFile(join(output, 'index.html'), 'utf8');
+    const { document } = parseHTML(html);
+    const scripts = document.querySelectorAll(
+      'script[src="/Incognito-Wiki/matomo-consent.js"]',
+    );
+    assert.equal(scripts.length, 1, 'every page should load one base-aware local controller');
+    assert.equal(scripts[0].hasAttribute('defer'), true);
+    await access(join(output, 'matomo-consent.js'));
+
+    const css = await collectCss(output);
+    assert.match(css, /#incognito-analytics-consent/);
+    assert.match(css, /\.incognito-consent-action/);
+    assert.match(css, /#incognito-privacy-settings/);
+  } finally {
+    await rm(output, { recursive: true, force: true });
+  }
+});