diff --git a/code/eleventy.config.js b/code/eleventy.config.js
index c0584ab..ae9fb63 100644
--- a/code/eleventy.config.js
+++ b/code/eleventy.config.js
@@ -1,9 +1,10 @@
-const path = require("path");
-
 module.exports = function (eleventyConfig) {
+  eleventyConfig.addGlobalData("site", { url: "https://code.moonweb.org" });
+  eleventyConfig.addFilter("date", (d) => d.toISOString());
   eleventyConfig.addPassthroughCopy({ "shared/theme-code.css": "theme.css" });
   eleventyConfig.addPassthroughCopy({ "shared/base.css": "shared-base.css" });
   eleventyConfig.addPassthroughCopy({ "shared/favicon/code.svg": "favicon.svg" });
+  eleventyConfig.addPassthroughCopy({ "code/robots.txt": "robots.txt" });
 
   return {
     dir: {
diff --git a/code/robots.txt b/code/robots.txt
new file mode 100644
index 0000000..f0bdb62
--- /dev/null
+++ b/code/robots.txt
@@ -0,0 +1,4 @@
+User-agent: *
+Allow: /
+
+Sitemap: https://code.moonweb.org/sitemap.xml
diff --git a/code/sitemap.xml.njk b/code/sitemap.xml.njk
new file mode 100644
index 0000000..7cbc214
--- /dev/null
+++ b/code/sitemap.xml.njk
@@ -0,0 +1,5 @@
+---
+permalink: /sitemap.xml
+eleventyExcludeFromCollections: true
+---
+{% include "sitemap.njk" %}
diff --git a/hub/eleventy.config.js b/hub/eleventy.config.js
index 42c4656..3246063 100644
--- a/hub/eleventy.config.js
+++ b/hub/eleventy.config.js
@@ -1,9 +1,10 @@
-const path = require("path");
-
 module.exports = function (eleventyConfig) {
+  eleventyConfig.addGlobalData("site", { url: "https://hub.moonweb.org" });
+  eleventyConfig.addFilter("date", (d) => d.toISOString());
   eleventyConfig.addPassthroughCopy({ "shared/theme-hub.css": "theme.css" });
   eleventyConfig.addPassthroughCopy({ "shared/base.css": "shared-base.css" });
   eleventyConfig.addPassthroughCopy({ "shared/favicon/hub.svg": "favicon.svg" });
+  eleventyConfig.addPassthroughCopy({ "hub/robots.txt": "robots.txt" });
 
   return {
     dir: {
diff --git a/hub/robots.txt b/hub/robots.txt
new file mode 100644
index 0000000..778be63
--- /dev/null
+++ b/hub/robots.txt
@@ -0,0 +1,4 @@
+User-agent: *
+Allow: /
+
+Sitemap: https://hub.moonweb.org/sitemap.xml
diff --git a/hub/sitemap.xml.njk b/hub/sitemap.xml.njk
new file mode 100644
index 0000000..7cbc214
--- /dev/null
+++ b/hub/sitemap.xml.njk
@@ -0,0 +1,5 @@
+---
+permalink: /sitemap.xml
+eleventyExcludeFromCollections: true
+---
+{% include "sitemap.njk" %}
diff --git a/infra/eleventy.config.js b/infra/eleventy.config.js
index f32b92f..3338af4 100644
--- a/infra/eleventy.config.js
+++ b/infra/eleventy.config.js
@@ -1,9 +1,10 @@
-const path = require("path");
-
 module.exports = function (eleventyConfig) {
+  eleventyConfig.addGlobalData("site", { url: "https://infra.moonweb.org" });
+  eleventyConfig.addFilter("date", (d) => d.toISOString());
   eleventyConfig.addPassthroughCopy({ "shared/theme-infra.css": "theme.css" });
   eleventyConfig.addPassthroughCopy({ "shared/base.css": "shared-base.css" });
   eleventyConfig.addPassthroughCopy({ "shared/favicon/infra.svg": "favicon.svg" });
+  eleventyConfig.addPassthroughCopy({ "infra/robots.txt": "robots.txt" });
 
   return {
     dir: {
diff --git a/infra/robots.txt b/infra/robots.txt
new file mode 100644
index 0000000..b9acb72
--- /dev/null
+++ b/infra/robots.txt
@@ -0,0 +1,4 @@
+User-agent: *
+Allow: /
+
+Sitemap: https://infra.moonweb.org/sitemap.xml
diff --git a/infra/sitemap.xml.njk b/infra/sitemap.xml.njk
new file mode 100644
index 0000000..7cbc214
--- /dev/null
+++ b/infra/sitemap.xml.njk
@@ -0,0 +1,5 @@
+---
+permalink: /sitemap.xml
+eleventyExcludeFromCollections: true
+---
+{% include "sitemap.njk" %}
diff --git a/retro/eleventy.config.js b/retro/eleventy.config.js
index d162dfd..729f1d4 100644
--- a/retro/eleventy.config.js
+++ b/retro/eleventy.config.js
@@ -1,9 +1,10 @@
-const path = require("path");
-
 module.exports = function (eleventyConfig) {
+  eleventyConfig.addGlobalData("site", { url: "https://retro.moonweb.org" });
+  eleventyConfig.addFilter("date", (d) => d.toISOString());
   eleventyConfig.addPassthroughCopy({ "shared/theme-retro.css": "theme.css" });
   eleventyConfig.addPassthroughCopy({ "shared/base.css": "shared-base.css" });
   eleventyConfig.addPassthroughCopy({ "shared/favicon/retro.svg": "favicon.svg" });
+  eleventyConfig.addPassthroughCopy({ "retro/robots.txt": "robots.txt" });
 
   return {
     dir: {
diff --git a/retro/robots.txt b/retro/robots.txt
new file mode 100644
index 0000000..b42cb4e
--- /dev/null
+++ b/retro/robots.txt
@@ -0,0 +1,4 @@
+User-agent: *
+Allow: /
+
+Sitemap: https://retro.moonweb.org/sitemap.xml
diff --git a/retro/sitemap.xml.njk b/retro/sitemap.xml.njk
new file mode 100644
index 0000000..7cbc214
--- /dev/null
+++ b/retro/sitemap.xml.njk
@@ -0,0 +1,5 @@
+---
+permalink: /sitemap.xml
+eleventyExcludeFromCollections: true
+---
+{% include "sitemap.njk" %}
diff --git a/shared/_includes/base.njk b/shared/_includes/base.njk
index 1dde114..37859c9 100644
--- a/shared/_includes/base.njk
+++ b/shared/_includes/base.njk
@@ -5,6 +5,14 @@
   <meta name="viewport" content="width=device-width, initial-scale=1">
   <title>{{ title }} · moonweb.org</title>
   <meta name="description" content="{{ description }}">
+  <link rel="canonical" href="{{ site.url }}{{ page.url }}">
+  <meta property="og:title" content="{{ title }} · moonweb.org">
+  <meta property="og:description" content="{{ description }}">
+  <meta property="og:url" content="{{ site.url }}{{ page.url }}">
+  <meta property="og:type" content="website">
+  <meta name="twitter:card" content="summary">
+  <meta name="twitter:title" content="{{ title }} · moonweb.org">
+  <meta name="twitter:description" content="{{ description }}">
   <link rel="icon" href="/favicon.svg" type="image/svg+xml">
   <link rel="preconnect" href="https://fonts.googleapis.com">
   <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
diff --git a/shared/_includes/sitemap.njk b/shared/_includes/sitemap.njk
new file mode 100644
index 0000000..e3e10a2
--- /dev/null
+++ b/shared/_includes/sitemap.njk
@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
+{%- for page in collections.all %}
+  <url>
+    <loc>{{ site.url }}{{ page.url }}</loc>
+    <lastmod>{{ page.date | date }}</lastmod>
+  </url>
+{%- endfor %}
+</urlset>
diff --git a/smarthome/eleventy.config.js b/smarthome/eleventy.config.js
index 81f7f12..2f0091a 100644
--- a/smarthome/eleventy.config.js
+++ b/smarthome/eleventy.config.js
@@ -1,9 +1,10 @@
-const path = require("path");
-
 module.exports = function (eleventyConfig) {
+  eleventyConfig.addGlobalData("site", { url: "https://smarthome.moonweb.org" });
+  eleventyConfig.addFilter("date", (d) => d.toISOString());
   eleventyConfig.addPassthroughCopy({ "shared/theme-smarthome.css": "theme.css" });
   eleventyConfig.addPassthroughCopy({ "shared/base.css": "shared-base.css" });
   eleventyConfig.addPassthroughCopy({ "shared/favicon/smarthome.svg": "favicon.svg" });
+  eleventyConfig.addPassthroughCopy({ "smarthome/robots.txt": "robots.txt" });
 
   return {
     dir: {
diff --git a/smarthome/robots.txt b/smarthome/robots.txt
new file mode 100644
index 0000000..b74da2a
--- /dev/null
+++ b/smarthome/robots.txt
@@ -0,0 +1,4 @@
+User-agent: *
+Allow: /
+
+Sitemap: https://smarthome.moonweb.org/sitemap.xml
diff --git a/smarthome/sitemap.xml.njk b/smarthome/sitemap.xml.njk
new file mode 100644
index 0000000..7cbc214
--- /dev/null
+++ b/smarthome/sitemap.xml.njk
@@ -0,0 +1,5 @@
+---
+permalink: /sitemap.xml
+eleventyExcludeFromCollections: true
+---
+{% include "sitemap.njk" %}