diff --git a/package-lock.json b/package-lock.json
index 01fe025..c892275 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -27,6 +27,8 @@
         "eslint": "^10.8.1",
         "eslint-config-prettier": "^10.1.8",
         "eslint-plugin-astro": "^3.1.0",
+        "hast-util-from-html": "^2.0.3",
+        "hast-util-to-text": "^4.0.2",
         "pagefind": "^1.5.2",
         "prettier": "^3.9.6",
         "prettier-plugin-astro": "^0.14.1",
@@ -40,7 +42,12 @@
         "remark-link-card": "^1.3.1",
         "remark-math": "^6.0.0",
         "remark-sectionize": "^2.1.0",
-        "typescript-eslint": "^8.67.0"
+        "typescript-eslint": "^8.67.0",
+        "unist-util-remove": "^4.0.0"
+      },
+      "devDependencies": {
+        "@types/hast": "^3.0.5",
+        "@types/unist": "^3.0.3"
       }
     },
     "node_modules/@antfu/install-pkg": {
@@ -10476,6 +10483,21 @@
         "url": "https://opencollective.com/unified"
       }
     },
+    "node_modules/unist-util-remove": {
+      "version": "4.0.0",
+      "resolved": "https://registry.npmjs.org/unist-util-remove/-/unist-util-remove-4.0.0.tgz",
+      "integrity": "sha512-b4gokeGId57UVRX/eVKej5gXqGlc9+trkORhFJpu9raqZkZhU0zm8Doi05+HaiBsMEIJowL+2WtQ5ItjsngPXg==",
+      "license": "MIT",
+      "dependencies": {
+        "@types/unist": "^3.0.0",
+        "unist-util-is": "^6.0.0",
+        "unist-util-visit-parents": "^6.0.0"
+      },
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/unified"
+      }
+    },
     "node_modules/unist-util-remove-position": {
       "version": "5.0.0",
       "resolved": "https://registry.npmjs.org/unist-util-remove-position/-/unist-util-remove-position-5.0.0.tgz",
diff --git a/package.json b/package.json
index cc97693..2d20723 100644
--- a/package.json
+++ b/package.json
@@ -30,6 +30,8 @@
     "eslint": "^10.8.1",
     "eslint-config-prettier": "^10.1.8",
     "eslint-plugin-astro": "^3.1.0",
+    "hast-util-from-html": "^2.0.3",
+    "hast-util-to-text": "^4.0.2",
     "pagefind": "^1.5.2",
     "prettier": "^3.9.6",
     "prettier-plugin-astro": "^0.14.1",
@@ -43,10 +45,15 @@
     "remark-link-card": "^1.3.1",
     "remark-math": "^6.0.0",
     "remark-sectionize": "^2.1.0",
-    "typescript-eslint": "^8.67.0"
+    "typescript-eslint": "^8.67.0",
+    "unist-util-remove": "^4.0.0"
   },
   "allowScripts": {
     "esbuild@0.28.2": true,
     "esbuild@0.25.4": true
+  },
+  "devDependencies": {
+    "@types/hast": "^3.0.5",
+    "@types/unist": "^3.0.3"
   }
 }
diff --git a/src/lib/excerpt.ts b/src/lib/excerpt.ts
new file mode 100644
index 0000000..ffdde6c
--- /dev/null
+++ b/src/lib/excerpt.ts
@@ -0,0 +1,31 @@
+import { fromHtml } from "hast-util-from-html";
+import { toText } from "hast-util-to-text";
+import { remove } from "unist-util-remove";
+import type { Node } from "unist";
+import type { Element } from "hast";
+
+function isHeadingAnchor(node: Node): node is Element {
+  const element = node as Element;
+  return (
+    node.type === "element" &&
+    element.tagName === "a" &&
+    Array.isArray(element.properties.className) &&
+    element.properties.className.includes("anchor")
+  );
+}
+
+/** Builds a short plain-text excerpt from an article's rendered HTML. */
+export function excerptFromHtml(html: string | undefined, maxLength = 120): string | undefined {
+  if (!html) return undefined;
+
+  const tree = fromHtml(html, { fragment: true });
+
+  // Drop the "#" anchor links rehype-autolink-headings appends to headings;
+  // they're navigation, not article content.
+  remove(tree, isHeadingAnchor);
+
+  const text = toText(tree).replace(/\s+/g, " ").trim();
+  if (!text) return undefined;
+  if (text.length <= maxLength) return text;
+  return `${text.slice(0, maxLength).trimEnd()}…`;
+}
diff --git a/src/pages/articles/[...slug].astro b/src/pages/articles/[...slug].astro
index b853659..6c90a86 100644
--- a/src/pages/articles/[...slug].astro
+++ b/src/pages/articles/[...slug].astro
@@ -6,6 +6,9 @@ import Loading from "../../components/Loading.astro";
 import { getCollection, render } from "astro:content";
 import type { CollectionEntry } from "astro:content";
 
+import { excerptFromHtml } from "../../lib/excerpt";
+import { SITE_DESCRIPTION } from "../../consts";
+
 export async function getStaticPaths() {
   const posts = await getCollection("articles");
   return posts.map((post) => ({
@@ -19,9 +22,12 @@ type Props = CollectionEntry<"articles">;
 const article = Astro.props;
 const { Content } = await render(article);
 
-const { title, description, pubDate, updatedDate, draft } = article.data;
+const { title, pubDate, updatedDate, draft } = article.data;
 const { url } = article.data;
 
+const description =
+  article.data.description ?? excerptFromHtml(article.rendered?.html) ?? SITE_DESCRIPTION;
+
 const ogImage = `${import.meta.env.BASE_URL}og/${article.id}.png`;
 ---
 
diff --git a/src/pages/og/[...slug].ts b/src/pages/og/[...slug].ts
index 7e6a196..de640b5 100644
--- a/src/pages/og/[...slug].ts
+++ b/src/pages/og/[...slug].ts
@@ -2,6 +2,7 @@ import { getCollection } from "astro:content";
 import { OGImageRoute } from "astro-og-canvas";
 
 import { SITE_NAME, SITE_DESCRIPTION } from "../../consts";
+import { excerptFromHtml } from "../../lib/excerpt";
 
 const articles = await getCollection("articles", ({ data }) => !data.draft);
 
@@ -10,7 +11,8 @@ const pages = Object.fromEntries(
     article.id,
     {
       title: article.data.title,
-      description: article.data.description ?? SITE_DESCRIPTION
+      description:
+        article.data.description ?? excerptFromHtml(article.rendered?.html) ?? SITE_DESCRIPTION
     }
   ])
 );