diff --git a/apps/svelte.dev/src/app.html b/apps/svelte.dev/src/app.html
index 4fcb830279..ea62d87f86 100644
--- a/apps/svelte.dev/src/app.html
+++ b/apps/svelte.dev/src/app.html
@@ -59,9 +59,9 @@
 				}
 			}
 
-			if (localStorage.getItem('svelte:prefers-ts') !== 'false') {
+			if (localStorage.getItem('svelte:prefers-ts') === 'false') {
 				for (const node of document.querySelectorAll('.ts-toggle')) {
-					node.checked = true;
+					node.checked = false;
 				}
 			}
 		</script>
diff --git a/packages/site-kit/src/lib/markdown/renderer.ts b/packages/site-kit/src/lib/markdown/renderer.ts
index 16bbf48e65..ba71f4aca9 100644
--- a/packages/site-kit/src/lib/markdown/renderer.ts
+++ b/packages/site-kit/src/lib/markdown/renderer.ts
@@ -171,7 +171,7 @@ export async function render_content_markdown(
 			}
 
 			if (converted) {
-				html += `<input class="ts-toggle" title="Toggle language" type="checkbox" aria-label="Toggle JS/TS">`;
+				html += `<input class="ts-toggle" checked title="Toggle language" type="checkbox" aria-label="Toggle JS/TS">`;
 			}
 
 			if (options.copy) {