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.NET Server SDK

Server vs. Client

These docs are for using our .NET SDK in a multi-user, server side context. For client side and single-user contexts, check out our .NET Client SDK or one of the other client SDKs for your client side applications.

Statsig server SDK for .NET applications. This SDK is open source and hosted on github.

The Basics

Get started in a few quick steps.

  1. Create a free account on
  2. Install the SDK
  3. Initialize the SDK
  4. Fetch Feature Gates, Dynamic Configs, or Experiments
  5. Log a custom event

Step 1 - Create a free account on

You could skip this for now, but you will need an SDK Key and some Feature Gates or Dynamic Configs to use with the SDK in just a minute.

Step 2 - Install the SDK

The package is hosted on Nuget. You can either install it from your Visual Studio's Nuget package manager, or through the NuGet CLI:

nuget install Statsig

Step 3 - Initialize the SDK

After installation, you will need to initialize the SDK using a Server Secret Key from the statsig console.


Do NOT embed your Server Secret Key in client side applications, or expose it in any external facing documents. However, if you accidentally exposed it, you can create a new one in Statsig console.

There is also an optional parameter options that allows you to pass in a StatsigOptions to customize the SDK.

using Statsig;
using Statsig.Server;

await StatsigServer.Initialize(
new StatsigOptions(new StatsigEnvironment(EnvironmentTier.Development)) // optional, use when needed to customize certain behaviors

initialize will perform a network request. After initialize completes, virtually all SDK operations will be synchronous1--the SDK will fetch updates from Statsig in the background, independently of your API calls.

Step 4 - Fetch Feature Gates, Dynamic Configs, or Experiments

Now that your SDK is initialized, let's fetch a Feature Gate. Feature Gates can be used to create logic branches in code that can be rolled out to different users from the Statsig Console. Gates are always CLOSED or OFF (think return false;) by default.

From this point on, all APIs will require you to specify the user (see Statsig user) associated with the request. For example, check a gate for a certain user like this:

var user = new StatsigUser { UserID = "some_user_id", Email = "" };
var useNewFeature = await StatsigServer.CheckGate(user, "use_new_feature");
if (useNewFeature)
// Gate is on, enable new feature
// Gate is off

Feature Gates can be very useful for simple on/off switches, with optional but advanced user targeting. However, if you want to be able send a different set of values (strings, numbers, and etc.) to your clients based on specific user attributes, e.g. country, Dynamic Configs can help you with that. The API is very similar to Feature Gates, but you get an entire json object you can configure on the server and you can fetch typed parameters from it. For example:

var config = await StatsigServer.GetConfig(user, "awesome_product_details");

// The 2nd parameter is the default value to be used in case the given parameter name does not exist on
// the Dynamic Config object. This can happen when there is a typo, or when the user is offline and the
// value has not been cached on the client.
string itemName = config.Get<string>("product_name", "Awesome Product v1");
double price = config.Get<double>("price", 10.0);
bool shouldDiscount = config.Get<bool>("discount", false);

Then we have Experiments, which you can use to run A/B/n experiments and use advanced features like layers (coming soon) to avoid collision and enable quicker iterations with parameter reuse.

var expConfig = await StatsigServer.GetExperiment(user, "new_user_promo");

string promoTitle = expConfig.Get<string>("title", "Welcome to Statsig! Use discount code WELCOME10OFF for 10% off your first purchase!");
double discount = expConfig.Get<double>("discount", 0.1);


double price = msrp * (1 - discount);
Asynchronous APIs

We mentioned earlier that after calling initialize most SDK APIs would run synchronously, so why are getConfig and checkGate asynchronous?

The main reason is that older versions of the SDK might not know how to interpret new types of gate conditions. In such cases the SDK will make an asynchronous call to our servers to fetch the result of a check. This can be resolved by upgrading the SDK, and we will warn you if this happens.

For more details, read our blog post about SDK evaluations. If you have any questions, please ask them in our Feedback Repository.

Step 5 - Log a custom event

Now that you have a Feature Gate or an Experiment set up, you may want to track some custom events and see how your new features or different experiment groups affect these events. This is super easy with Statsig - simply call the Log Event API and specify the user and event name to log; you additionally provide some value and/or an object of metadata to be logged together with the event:

StatsigServer.LogEvent(user, "add_to_cart", "SKU_12345", new Dictionary<string, string>() { { "price", "9.99" }, { "item_name", "diet_coke_48_pack" } });

Statsig User

When calling APIs that require a user, you should pass as much information as possible in order to take advantage of advanced gate and config conditions (like country or OS/browser level checks), and correctly measure impact of your experiments on your metrics/events. The userID field is required because it's needed to provide a consistent experience for a given user (click here to understand further why it's important to always provide a userID).

Besides userID, we also have email, ip, userAgent, country, locale and appVersion as top-level fields on StatsigUser. In addition, you can pass any key-value pairs in an object/dictionary to the custom field and be able to create targeting based on them.

Have sensitive user PII data that should not be logged?

No problem, we have a solution for it! On the StatsigUser object we also have a field called privateAttributes, which is a simple object/dictionary that you can use to set private user attributes. Any attribute set in privateAttributes will only be used for evaluation/targeting, and removed from any logs before they are sent to Statsig server.

For example, if you have feature gates that should only pass for users with emails ending in "", but do not want to log your users' email addresses to Statsig, you can simply add the key-value pair { email: "" } to privateAttributes on the user and that's it!

Statsig Options

Initialize() takes an optional parameter options in addition to sdkKey and user that you can provide to customize the Statsig client. Here are the current options and we are always adding more to the list:

  • environment: StatsigEnvironment, default null
    • An object you can use to set environment variables that apply to all of your users in the same session and will be used for targeting purposes.
    • The most common usage is to set the environment tier (EnvironmentTier), e.g. new StatsigEnvironment(EnvironmentTier.Staging), and have feature gates pass/fail for specific environments.

Shutting down Statsig

Because we batch and periodically flush events, some events may not have been sent when your app/server shuts down. To make sure all logged events are properly flushed, you should tell Statsig to shutdown when your app/server is closing:



Type StatsigUser

namespace Statsig
public class StatsigUser
public string? UserID
public string? Email
public string? IPAddress
public string? UserAgent
public string? Country
public string? Locale
public string? AppVersion

public StatsigUser()

public void AddCustomProperty(string key, object value)

public void AddPrivateAttribute(string key, object value)

public void AddCustomID(string idType, string value)


Type StatsigOptions

namespace Statsig
public class StatsigOptions
public string ApiUrlBase { get; }
public StatsigEnvironment StatsigEnvironment { get; }
public string? PersistentStorageFolder { get; set; }
public double RulesetsSyncInterval = 60;
public double IDListsSyncInterval = 60;
public int ClientRequestTimeoutMs = 0;

private Dictionary<string, string> _additionalHeaders;
private Func<IIDStore>? _idStoreFactory = null;

public StatsigOptions(string? apiUrlBase = null, StatsigEnvironment? environment = null)


How do I run experiments for logged out users?

You can run experiments for arbitrary unit IDs (sessionID, groupID, etc), rather than at the userID level, if you choose. These custom unit IDs must be predefined in your Statsig project, and then selected in the Experiment creation flow. For more information, see our guide on experimenting on custom ID types