diff --git a/src/components/Markdown.svelte b/src/components/Markdown.svelte
index ee0fb293a..2d3d5f241 100644
--- a/src/components/Markdown.svelte
+++ b/src/components/Markdown.svelte
@@ -98,8 +98,14 @@
   }
 
   afterUpdate(async () => {
-    // Don't underline <a> tags that contain images.
     for (const e of container.querySelectorAll("a")) {
+      if (URL.canParse(e.href)) {
+        const url = new URL(e.href);
+        if (url.origin !== window.origin) {
+          e.target = "_blank";
+        }
+      }
+      // Don't underline <a> tags that contain images.
       if (e.firstElementChild instanceof HTMLImageElement) {
         e.classList.add("no-underline");
       }
diff --git a/src/lib/markdown.ts b/src/lib/markdown.ts
index ba9c2ae71..2bae17a50 100644
--- a/src/lib/markdown.ts
+++ b/src/lib/markdown.ts
@@ -140,11 +140,10 @@ export class Renderer extends BaseRenderer {
       // By lowercasing we avoid casing mismatches, between headings and links.
       return `<a href="${href.toLowerCase()}">${text}</a>`;
     } else {
-      try {
-        href = new URL(href, this.#baseUrl).href;
-      } catch {
-        // Use original href value
-      }
+      href = URL.canParse(href, this.#baseUrl)
+        ? new URL(href, this.#baseUrl).href
+        : href;
+
       return `<a href="${href}">${text}</a>`;
     }
   }
diff --git a/tests/e2e/project.spec.ts b/tests/e2e/project.spec.ts
index 1b885aa60..c4356fc46 100644
--- a/tests/e2e/project.spec.ts
+++ b/tests/e2e/project.spec.ts
@@ -449,13 +449,15 @@ test.describe("browser error handling", () => {
   });
 });
 
-test("external markdown link", async ({ page }) => {
+test("external markdown link", async ({ context, page }) => {
   await page.route("https://example.com/**", route => {
     return route.fulfill({ body: "hello", contentType: "text/plain" });
   });
   await page.goto(`${markdownUrl}/tree/main/footnotes.md`);
+  const pagePromise = context.waitForEvent("page");
   await page.getByRole("link", { name: "https://example.com" }).click();
-  await expect(page).toHaveURL("https://example.com");
+  const newPage = await pagePromise;
+  await expect(newPage).toHaveURL("https://example.com");
 });
 
 test("internal file markdown link", async ({ page }) => {