> ## Documentation Index > Fetch the complete documentation index at: https://mintlify.com/App-vNext/Polly/llms.txt > Use this file to discover all available pages before exploring further. # Introduction > A .NET resilience and transient-fault-handling library for building fault-tolerant applications Polly is a powerful .NET resilience and transient-fault-handling library that allows developers to express resilience strategies such as Retry, Circuit Breaker, Hedging, Timeout, Rate Limiter, and Fallback in a fluent and thread-safe manner. Polly is part of the [.NET Foundation](https://www.dotnetfoundation.org/about) and supports .NET Standard 1.1, 2.0+, .NET Core, .NET Framework, and .NET 6+. ## What is Polly? Modern applications often depend on external services, databases, and APIs that can fail temporarily or become unavailable. Polly helps you handle these transient faults gracefully by providing a comprehensive set of resilience strategies that you can combine and configure to match your specific requirements. With Polly, you can: * **Retry operations** that fail due to transient faults * **Break circuits** when a system is under stress to prevent cascading failures * **Add timeouts** to prevent operations from hanging indefinitely * **Rate limit** requests to protect your services from overload * **Provide fallback values** when operations fail * **Hedge requests** by executing parallel operations and taking the fastest response * **Inject chaos** to test your application's resilience ## Key Features Automatically retry failed operations with exponential backoff and jitter Prevent cascading failures by breaking the circuit when fault thresholds are exceeded Set time limits on operations to prevent them from running indefinitely Control the rate of requests with multiple rate limiting algorithms Provide alternative values or actions when operations fail Execute parallel actions and use the fastest successful response Test your application's resilience by injecting controlled faults Built-in telemetry and monitoring for all resilience strategies ## How Polly Works Polly uses a **resilience pipeline** pattern that combines one or more **resilience strategies** into a unified execution flow. You build pipelines using a fluent builder API: ```csharp theme={null} // Create a resilience pipeline with retry and timeout strategies ResiliencePipeline pipeline = new ResiliencePipelineBuilder() .AddRetry(new RetryStrategyOptions { MaxRetryAttempts = 3, Delay = TimeSpan.FromSeconds(1), BackoffType = DelayBackoffType.Exponential }) .AddTimeout(TimeSpan.FromSeconds(10)) .Build(); // Execute your code through the pipeline await pipeline.ExecuteAsync(async token => { // Your code here - Polly handles retries, timeouts, etc. return await httpClient.GetAsync("https://api.example.com/data", token); }); ``` ## NuGet Packages Polly is distributed as a set of NuGet packages: | Package | Purpose | | ---------------------- | ---------------------------------------------------- | | **Polly.Core** | Core abstractions and built-in resilience strategies | | **Polly.Extensions** | Dependency injection and telemetry integration | | **Polly.RateLimiting** | Integration with System.Threading.RateLimiting APIs | | **Polly.Testing** | Testing utilities for Polly pipelines | | **Polly** | Legacy v7 API for backward compatibility | This documentation covers Polly v8, which introduces a new, more powerful API. If you're using Polly v7, see the [migration guide](/migration/v8-migration-guide). ## Why Choose Polly? Polly is used by thousands of applications worldwide, including Microsoft's own services. It has been refined over years of production use. Combine multiple resilience strategies in any order to create sophisticated fault-handling behaviors tailored to your needs. Designed for high-performance scenarios with minimal allocation and overhead. Supports async/await throughout. Built-in support for logging, metrics, and distributed tracing to help you understand your application's resilience. First-class support for Microsoft.Extensions.DependencyInjection with lifecycle management and configuration. Create custom resilience strategies to address unique requirements in your application. ## Next Steps Install Polly and set up your first project Build your first resilience pipeline in minutes Learn about resilience pipelines and strategies Explore the complete API documentation