diff --git a/hugo-site/static/js/donation-success.js b/hugo-site/static/js/donation-success.js
index 9ab3cd78..454d0a7a 100644
--- a/hugo-site/static/js/donation-success.js
+++ b/hugo-site/static/js/donation-success.js
@@ -281,7 +281,10 @@ function displayCertificate(armoredCertificate, armoredSigningKey) {
         const certB64 = urlSafeBase64(armoredCertificate);
         const skB64 = urlSafeBase64(armoredSigningKey);
         const contractId = 'DLog47hEsrtuGT4N5XCeMBG45m4n1aWM89tBZXue2E1N';
-        const importUrl = `http://127.0.0.1:7509/v1/contract/web/${contractId}/#import=${certB64}.${skB64}`;
+        // Use localhost rather than the literal 127.0.0.1: the node binds its
+        // API on the IPv6 loopback by default, so on Windows "localhost" (::1)
+        // is reachable while the literal IPv4 address is refused.
+        const importUrl = `http://localhost:7509/v1/contract/web/${contractId}/#import=${certB64}.${skB64}`;
         window.open(importUrl, '_blank');
       });
     }
diff --git a/hugo-site/themes/freenet/layouts/shortcodes/river-invite-button.html b/hugo-site/themes/freenet/layouts/shortcodes/river-invite-button.html
index 77ff8a56..498817fd 100644
--- a/hugo-site/themes/freenet/layouts/shortcodes/river-invite-button.html
+++ b/hugo-site/themes/freenet/layouts/shortcodes/river-invite-button.html
@@ -156,7 +156,11 @@
 <script>
 document.addEventListener('DOMContentLoaded', function() {
     const apiUrl = window.ghostkeyApiUrl;
-    const riverBaseUrl = 'http://127.0.0.1:7509/v1/contract/web/raAqMhMG7KUpXBU2SxgCQ3Vh4PYjttxdSWd9ftV7RLv/';
+    // Use localhost rather than the literal 127.0.0.1 so the link works on
+    // Windows: the node binds its API on the IPv6 loopback by default, and
+    // Windows resolves "localhost" to ::1 (reachable) while the literal IPv4
+    // address is refused. localhost is reachable on every platform.
+    const riverBaseUrl = 'http://localhost:7509/v1/contract/web/raAqMhMG7KUpXBU2SxgCQ3Vh4PYjttxdSWd9ftV7RLv/';
 
     const getInviteBtn = document.getElementById('get-invite-btn');
     const inviteForm = document.getElementById('invite-form');