diff --git a/examples/index.html b/examples/index.html
index cbb4c4c..a58bd9b 100644
--- a/examples/index.html
+++ b/examples/index.html
@@ -19,6 +19,7 @@ <h1>Gist for Web</h1>
       <a href="#" class="button" onClick="embedBanner()">Embed Banner</a>
       <a href="#" class="button" onClick="embedFloatingMessage()">Embed Floating Message</a>
       <a href="#" class="button" onClick="embedHTMLFloatingMessage()">Embed HTML Floating Message</a>
+      <a href="#" class="button" onClick="addAnonymousCustomAttribute()">Set Anonymous Custom Attribute</a>
       <a href="#" class="button" onClick="logIn()">Log In</a>
       <a href="#" class="button" onClick="logOut()">Log Out</a>
     </div>
@@ -32,7 +33,7 @@ <h1>Gist for Web</h1>
         Dev Setup Options
         { siteId: "siteid", dataCenter: "us", env: "dev", logging: true }
       */
-      Gist.setup({ siteId: "a5ec106751ef4b34a0b9", dataCenter: "eu", logging: true, env: "prod" });
+      Gist.setup({ siteId: "a5ec106751ef4b34a0b9", dataCenter: "eu", logging: true, env: "prod", useAnonymousSession: true });
       Gist.setUserToken("ABC123");
       Gist.setCurrentRoute("home");
 
@@ -116,6 +117,10 @@ <h1>Gist for Web</h1>
             }
           }, "x-gist-floating-bottom-right");
       }
+
+      function addAnonymousCustomAttribute() {
+        Gist.setCustomAttribute("cio_anonymous_id", "123456");
+      }
     </script>
   </body>
 </html>
\ No newline at end of file
diff --git a/src/gist.js b/src/gist.js
index fa86f72..e38dc45 100644
--- a/src/gist.js
+++ b/src/gist.js
@@ -4,6 +4,7 @@ import { startQueueListener, checkMessageQueue, stopSSEListener } from "./manage
 import { setUserToken, clearUserToken, useGuestSession } from "./managers/user-manager";
 import { showMessage, embedMessage, hideMessage, removePersistentMessage, fetchMessageByInstanceId, logBroadcastDismissedLocally } from "./managers/message-manager";
 import { setUserLocale } from "./managers/locale-manager";
+import { setCustomAttribute, clearCustomAttributes, removeCustomAttribute } from "./managers/custom-attribute-manager";
 import { setupPreview } from "./utilities/preview-mode";
 
 export default class {
@@ -58,6 +59,18 @@ export default class {
     setUserLocale(userLocale);
   }
 
+  static setCustomAttribute(key, value) {
+    return setCustomAttribute(key, value);
+  }
+
+  static clearCustomAttributes() {
+    clearCustomAttributes();
+  }
+
+  static removeCustomAttribute(key) {
+    return removeCustomAttribute(key);
+  }
+
   static async clearUserToken() {
     if (this.config.isPreviewSession) return;
     clearUserToken();
diff --git a/src/managers/custom-attribute-manager.js b/src/managers/custom-attribute-manager.js
new file mode 100644
index 0000000..698b6b3
--- /dev/null
+++ b/src/managers/custom-attribute-manager.js
@@ -0,0 +1,82 @@
+import { log } from '../utilities/log';
+import { setKeyToLocalStore, getKeyFromLocalStore, clearKeyFromLocalStore } from '../utilities/local-storage';
+
+const customAttributesLocalStoreName = "gist.web.customAttributes";
+const defaultExpiryInDays = 30;
+
+// Internal map to store custom attributes in memory
+let customAttributesMap = new Map();
+
+function loadCustomAttributesFromStorage() {
+  const storedAttributes = getKeyFromLocalStore(customAttributesLocalStoreName);
+  if (storedAttributes) {
+    try {
+      customAttributesMap = new Map(storedAttributes);
+    } catch {
+      customAttributesMap = new Map();
+    }
+  } else {
+    customAttributesMap = new Map();
+  }
+}
+
+function saveCustomAttributesToStorage() {
+  const attributesArray = Array.from(customAttributesMap.entries());
+  const expiryDate = new Date();
+  expiryDate.setDate(expiryDate.getDate() + defaultExpiryInDays);
+  
+  setKeyToLocalStore(customAttributesLocalStoreName, attributesArray, expiryDate);
+  log(`Saved ${customAttributesMap.size} custom attributes to storage with TTL of ${defaultExpiryInDays} days`);
+}
+
+loadCustomAttributesFromStorage();
+
+export function setCustomAttribute(key, value) {
+  if (!key || typeof key !== 'string') {
+    log(`Invalid key for custom attribute: ${key}`);
+    return false;
+  }
+  
+  customAttributesMap.set(key, value);
+  saveCustomAttributesToStorage();
+  log(`Set custom attribute "${key}" to "${value}"`);
+  return true;
+}
+
+export function getCustomAttribute(key) {
+  if (!key || typeof key !== 'string') {
+    log(`Invalid key for custom attribute: ${key}`);
+    return null;
+  }
+  
+  return customAttributesMap.get(key) || null;
+}
+
+export function getAllCustomAttributes() {
+  return new Map(customAttributesMap);
+}
+
+export function clearCustomAttributes() {
+  customAttributesMap.clear();
+  clearKeyFromLocalStore(customAttributesLocalStoreName);
+  log(`Cleared all custom attributes`);
+}
+
+export function removeCustomAttribute(key) {
+  if (!key || typeof key !== 'string') {
+    log(`Invalid key for custom attribute: ${key}`);
+    return false;
+  }
+  
+  const existed = customAttributesMap.has(key);
+  customAttributesMap.delete(key);
+  
+  if (customAttributesMap.size > 0) {
+    saveCustomAttributesToStorage();
+  } else {
+    clearKeyFromLocalStore(customAttributesLocalStoreName);
+  }
+  
+  log(`Removed custom attribute "${key}"`);
+  return existed;
+}
diff --git a/src/managers/message-manager.js b/src/managers/message-manager.js
index 6b6180b..d9d2d34 100644
--- a/src/managers/message-manager.js
+++ b/src/managers/message-manager.js
@@ -18,6 +18,7 @@ import {
 } from "./message-component-manager";
 import { resolveMessageProperties } from "./gist-properties-manager";
 import { positions, addPageElement } from "./page-component-manager";
+import { getAllCustomAttributes } from "./custom-attribute-manager";
 import { checkMessageQueue } from "./queue-manager";
 import { isMessageBroadcast, markBroadcastAsSeen, markBroadcastAsDismissed } from './message-broadcast-manager';
 import { markUserQueueMessageAsSeen } from './message-user-queue-manager';
@@ -126,7 +127,8 @@ function loadMessageComponent(message, elementId = null) {
     messageId: message.messageId,
     instanceId: message.instanceId,
     livePreview: false,
-    properties: message.properties
+    properties: message.properties,
+    customAttributes: Object.fromEntries(getAllCustomAttributes())
   }
   var url = `${settings.GIST_VIEW_ENDPOINT[Gist.config.env]}/index.html`
   window.addEventListener('message', handleGistEvents);