LocalStack.NET

LocalStack is a local AWS cloud emulator. LocalStack.NET wires AWS SDK for .NET v4 clients to LocalStack and lets you switch between LocalStack and real AWS with one configuration setting. LocalStack's .NET guide lists LocalStack.NET as an alternative to configuring endpoints by hand.

• Create LocalStack-configured AWS clients without manual endpoint code.
• Register clients through dependency injection with APIs that mirror AWSSDK.Extensions.NETCore.Setup.
• Switch client creation between LocalStack and AWS with LocalStack:UseLocalStack.
• Use Native AOT and trimming on net10.0 and net11.0 without changing consumer code.
• Run on .NET Framework 4.7.2 and later, and on other netstandard2.0 runtimes.

Install one package, plus the AWS SDK v4 service packages your app uses (for example, AWSSDK.S3). Extensions already depends on Core.

dotnet add package LocalStack.Client.Extensions   # configuration and dependency injection
dotnet add package LocalStack.Client              # Core only

Development builds are published to GitHub Packages at the feed shown below. Authentication requires a GitHub personal access token with read:packages permission. Replace the username and token placeholders below with your GitHub credentials.

dotnet nuget add source https://nuget.pkg.github.com/localstack-dotnet/index.json \
  --name github-localstack --username YOUR_GITHUB_USERNAME --password YOUR_GITHUB_TOKEN \
  --store-password-in-clear-text
dotnet add package LocalStack.Client.Extensions --prerelease --source github-localstack

.NET 11 is not generally available yet; the net11.0 assets are built with a .NET 11 preview SDK. .NET 8 and .NET 9 apps use both packages' netstandard2.0 assets under JIT, without Native AOT; both runtimes reach end of support on November 10, 2026.

Run LocalStack with Docker or docker-compose; follow the installation guide.

From 2026.03.0 on, every LocalStack for AWS image (including localstack/localstack:latest) needs LOCALSTACK_AUTH_TOKEN, even on the Hobby plan, which is free for non-commercial use. The token belongs to the container: LocalStack.NET does not read it, and it is not an AWS credential. localstack/localstack:4.14.0 is the last image that starts without a token; it receives no further updates. See the official auth-token documentation and CI guidance.

In a minimal-hosting Program.cs, register LocalStack and your AWS service interfaces:

using Amazon.S3;
using LocalStack.Client.Extensions;
using Microsoft.AspNetCore.Builder;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddLocalStack(builder.Configuration);
builder.Services.AddDefaultAWSOptions(builder.Configuration.GetAWSOptions());
builder.Services.AddAwsService<IAmazonS3>();

var app = builder.Build();
app.Run();

appsettings.Development.json selects LocalStack:

{
  "LocalStack": {
    "UseLocalStack": true,
    "Session": {
      "RegionName": "eu-central-1"
    },
    "Config": {
      "LocalStackHost": "localhost.localstack.cloud",
      "EdgePort": 4566
    }
  }
}

appsettings.Production.json selects the ordinary AWS SDK factory:

{
  "LocalStack": {
    "UseLocalStack": false
  },
  "AWS": {
    "Profile": "<your aws profile>",
    "Region": "eu-central-1"
  }
}

LocalStack does not validate the dummy session credentials. When UseLocalStack is false, the ordinary AWS section and AddDefaultAWSOptions(configuration.GetAWSOptions()) from AWSSDK.Extensions.NETCore.Setup apply.

AddAwsService<TService>, TryAddAwsService<TService>, AddAWSServiceLocalStack<TService>, and TryAddAWSServiceLocalStack<TService> each have two overloads:

• (ServiceLifetime lifetime = ServiceLifetime.Singleton, bool useServiceUrl = false)
• (AWSOptions? options, ServiceLifetime lifetime = ServiceLifetime.Singleton, bool useServiceUrl = false)

The Try* methods register a client only if its service type is not registered yet. AddAWSServiceLocalStack is an alias of AddAwsService that avoids confusion with the AWS SDK's AddAWSService. AddDefaultAwsOptions(AWSOptions) delegates to the SDK's AddDefaultAWSOptions.

Every LocalStack client gets the configured session credentials (dummy values by default), ProxyHost/ProxyPort pointing at LocalStack, HTTP unless UseSsl is true, and S3 path-style addressing. With useServiceUrl: false, the client also gets RegionEndpoint from RegionName, which must be set; useServiceUrl: true sets ServiceURL to the service's LocalStack URL instead. This option configures a LocalStack client; LocalStack:UseLocalStack selects LocalStack or AWS client creation.

builder.Services.TryAddAwsService<IAmazonS3>(
    lifetime: ServiceLifetime.Singleton, useServiceUrl: true);

Create a session with SessionStandalone and choose an implementation-based or interface-based client:

using Amazon.S3;
using LocalStack.Client;
using LocalStack.Client.Options;

var session = SessionStandalone.Init()
    .WithSessionOptions(new SessionOptions())
    .WithConfigurationOptions(new ConfigOptions())
    .Create();

using var s3 = session.CreateClientByImplementation<AmazonS3Client>();
using var s3ByInterface = session.CreateClientByInterface<IAmazonS3>();

The Type-based overloads are CreateClientByImplementation(Type implType, bool useServiceUrl = false) and CreateClientByInterface(Type serviceInterfaceType, bool useServiceUrl = false).

On net10.0 and net11.0, both packages support Native AOT and trimming with no consumer code changes, zero trim/AOT warnings and no suppressions. They use no runtime reflection for AWS SDK service clients and configs, or for custom clients that follow the SDK's shape; other client types keep a reflection fallback that runs only under JIT. The Type-based APIs rely on a source generator that runs in C# projects, so F# and Visual Basic apps should use the generic APIs under Native AOT. These statements cover LocalStack.NET's own code; the AWS SDK and LocalStack's service coverage have their own status. See platform and packaging for the exact boundary.

3.x (AWS SDK v4) is the supported line, developed on master; earlier versions are not supported. .NET 8 and .NET 9 apps use the netstandard2.0 assets under JIT, without Native AOT. See the changelog for release details and the security policy for the patch policy.

• SNS with LocalStack v3.7.2 through v3.8.1: SNS operations failed on LocalStack v3.7.2 and v3.8.0 because of a request-forwarding bug (issue #11652). The fix (PR #11653) was merged after v3.8.1 shipped and first appears in v4.0.0; no 3.x release contains it. Use LocalStack v4.0.0 or later, or v3.7.1 if you must stay on the 3.x line.
• Endpoint environment variables: With UseLocalStack: true, the LocalStack proxy settings took precedence over AWS_ENDPOINT_URL in a reported SQS case; with UseLocalStack: false, AWS_ENDPOINT_URL applied. The library defines no general precedence rule for AWS_ENDPOINT_URL or AWS_SERVICE_URL, so check the actual SDK configuration before relying on either. See #27.

See the contribution guide for build, sandbox, and test instructions. Ask questions and share ideas in Discussions.

Read the changelog for changes in each release.

LocalStack.NET uses the MIT License.