---
title: Session handling in visitor group criteria
slug: cms-11/dev-docs/session-handling-in-visitor-group-criteria
docTags: 
createdAt: 2026-07-22T19:45:16.749Z
---

:::hint{type="info"}
**Note**
This content applies to Optimizely Content Management System (CMS) versions 11.9.0 and higher.
:::

You can use the built-in Optimizely visitor group criteria without requiring session state on the server side by manually turning off ASP.NET session states. The visitor group system can autodetect if the session state was disabled and switch to a cookie-based approach for visitor group criteria that previously used sessions. You can also customize the storage of users' visitor group sessions.

### RaiseStartSession event

If the session is enabled, then the `RaiseStartSession` event is raised by `AspNet` session start event. If the session is disabled, then the `RaiseStartSession` event is raised by `HttpApplication` `AcquireRequestState` event.

### Session State

The session-based visitor group criterion saves its session state inside a session, cookie, or customized state storage. If the session is enabled and there is no registered custom storage, then it uses the HTTP session object as storage. If the session is disabled and there is no registered custom storage, then it uses the HTTP cookie as storage.

### Enable and disable session state

By default, CMS uses the HTTP session object if the `AspNet` session state mode is not **Off**. You can change it explicitly by setting the property `EnableSession` to false on the `VisitorGroupOptions` options.

### Customize State storage

To customize storage, implement the `IStateStorage` interface and register it. This sample code shows customized state storage and disabling session state.

```csharp
internal class InMemoryStateStorage: IStateStorage {
  IDictionary<string, string> _states = new Dictionary<string, string>();
  public bool IsAvailable => true;
  public object Load(string key) {
    _states.TryGetValue(key, out string value);
    return value;
  }

  public void Save(string key, object value) {
    _states[key] = (string) value;
  }

  public void Delete(string key) {
    _states.Remove(key);
  }
}
```

and you can register the custom state storage in `IServiceCollection` in the startup, like this:

```csharp
public class Startup {
  public void ConfigureServices(IServiceCollection services) {
    services.Add<VisitorGroupOptions>((s) => new VisitorGroupOptions(), ServiceInstanceScope.Singleton);
    services.Configure<VisitorGroupOptions>(s => s.EnableSession = EnableSession);
    services.Add<IStateStorage>(s => new InMemoryStateStorage(), ServiceInstanceScope.Singleton);
  }
}
```