diff --git a/functions/api/links/update.js b/functions/api/links/update.js
new file mode 100644
index 0000000..adc9dfb
--- /dev/null
+++ b/functions/api/links/update.js
@@ -0,0 +1,25 @@
+export async function onRequestPost({ request, env }) {
+    try {
+        const { 'g-recaptcha-response': token, ...body } = await request.json();
+        const vR = await fetch("https://www.google.com/recaptcha/api/siteverify", { method: "POST", headers: { "Content-Type": "application/x-www-form-urlencoded" }, body: `secret=${env.RECAPCHA_KEY}&response=${token}` });
+        if (!(await vR.json()).success) return new Response("CAPTCHA verification failed.", { status: 403 });
+
+        const { slug, destination_url, username, pass_hash } = body;
+        if (!slug || !destination_url || !username || !pass_hash) return new Response("Missing fields", { status: 400 });
+
+        const user = await env.D1_EV.prepare("SELECT pass_hash, custom_slugs FROM users WHERE username = ?").bind(username).first();
+        if (user?.pass_hash !== pass_hash) return new Response("Invalid credentials", { status: 401 });
+
+        let slugs = [];
+        try { slugs = JSON.parse(user.custom_slugs) } catch {}
+        if (!Array.isArray(slugs) || !slugs.includes(slug)) return new Response("Unauthorized", { status: 403 });
+
+        let url = destination_url.startsWith("http") ? destination_url : `https://${destination_url}`;
+        try { new URL(url) } catch { return new Response("Invalid destination URL", { status: 400 }) }
+
+        await env.KV_EV.put(slug, url.replace(/^https?:\/\//, ""));
+        return Response.json({ success: true });
+    } catch (e) {
+        return new Response(e.message, { status: 500 });
+    }
+}