HttpRequest.AnonymousID Property

Note: This property is new in the .NET Framework version 2.0.

Gets the anonymous identifier for the user, if present.

Namespace: System.Web
Assembly: System.Web (in system.web.dll)

public string AnonymousID { get; }
/** @property */
public String get_AnonymousID ()

public function get AnonymousID () : String

Property Value

A string representing the current anonymous user identifier.

The AnonymousId property assigns a long-lived unique identifier to a non-authenticated user, which can be used to track the user or assign profile properties to that user without storing data in a Session object. By default, the AnonymousId is tracked using a cookie but it can be set to use the URI when the Cookieless attribute in the anonymous identification configuration section is set to either the UseUri, UseDeviceProfile, or AutoDetect value. You must explicitly clear the cookie if you no longer want it available, for example when an anonymous user is authenticated.

Anonymous identification is used when there is a need to identify entities that are not authenticated and when authorization is required. For more information, see anonymousIdentification Element (ASP.NET Settings Schema)

The following code example demonstrates how to use the AnonymousId property by accessing the AnonymousIdentification_OnCreate event in the Global.asax file. This example has two parts:

  • A Web Forms page.

  • An method that handles the AnonymousIdentification_OnCreate event.

The first part of the code example shows how to use the AnonymousId property by accessing the AnonymousIdentification_OnCreate event in the Global.asax file. The AnonymousIdentification_OnCreate event is raised whenever a new anonymous ID is created.

<%@ Page Language="C#" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "">

<script runat="server">
  void Page_Load(object sender, EventArgs e)
      if (Application["UserCount"] != null)
          lblUserCount.Text = Application["UserCount"].ToString();
          lblCurrentUser.Text = Request.AnonymousID;

<html xmlns="" >
<head runat="server">
    <title>AnonymousID Example</title>
    <form id="form1" runat="server">
        Number of users: 
        <asp:Label ID="lblUserCount" Runat="server"></asp:Label><br />
    Current user:
        <asp:Label ID="lblCurrentUser" Runat="server"></asp:Label><br />

The second part of the code example shows how to display the new AnonymousId created by the AnonymousIdentification_OnCreate event in the preceding example.

void Application_Start(Object sender, EventArgs e)
        // Initialize user count property
        Application["UserCount"] = 0;
public void AnonymousIdentification_OnCreate(Object sender, AnonymousIdentificationEventArgs e)
    // Change the anonymous id
    e.AnonymousID = "mysite.com_Anonymous_User_" + DateTime.Now.Ticks;

    // Increment count of unique anonymous users
    Application["UserCount"] = Int32.Parse(Application["UserCount"].ToString()) + 1;

Windows 98, Windows 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0

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