What is the ASP.NET_SessionId cookie?
Maintains a user's session state across page requests in ASP.NET web applications.
Table of Contents
About ASP.NET_SessionId
| Vendor | Microsoft |
|---|---|
| Category Category The functional category of the technology, such as Web Analytics or Social Media. Learn more | Site Infrastructure & Security |
| Consent Category Consent Category The consent category this cookie most commonly falls under across sites we scan, normalized into four standard categories. Learn more | Strictly Necessary |
| Prevalence | Very Common |
| Popularity Popularity Popularity is calculated from our dataset of 4.5B+ cookies analyzed across hundreds of millions of web pages. Learn more | Found on 12.8% of scanned pages |
| Expiration Type | Session |
| Party Type Party Type Whether the cookie is first-party or third-party. Learn more | Mixed |
| Risk Level Risk Level Rates how sensitive the data stored by this cookie is (High, Medium, or Low) based on data classification and distribution. Learn more | Low |
| Vendor Privacy Policy | https://privacy.microsoft.com/en-us/privacystatement |
| Vendor Website | https://www.microsoft.com |
What is the purpose of ASP.NET_SessionId?
The ASP.NET_SessionId cookie is a native component of Microsoft's ASP.NET framework. It contains a randomly generated 24-character string (encoded with lowercase letters and numbers) that serves as a unique session identifier. This identifier allows the web server to associate consecutive HTTP requests from the same browser with a specific session state stored on the server.
Developers use this session state to temporarily persist data across page navigations, such as user preferences, authentication status, or shopping cart contents. By default, the cookie is sent with every request to the ASP.NET application and is discarded once the browser session ends.
What are the Privacy Risks of ASP.NET_SessionId?
Risk Level: Low
The cookie contains only a randomly generated alphanumeric identifier and does not natively store any personally identifiable information (PII) on the client side. It serves merely as a reference to data stored securely on the server. While session IDs can be subject to hijacking if not properly secured with HTTPS, the cookie itself is ephemeral and presents a low privacy risk.
How to Remove ASP.NET_SessionId from a Website
Website administrators can remove or alter this cookie by modifying the ASP.NET application's configuration. To disable the cookie entirely and rely on cookieless sessions (where the session ID is embedded in the URL), administrators can set the cookieless attribute of the sessionState element to true in the Web.config file. If session state is not required at all, it can be disabled application-wide by setting <sessionState mode="Off" />.