What is Siege?

Siege is a free and open source HTTP load testing and benchmarking tool that is designed to stress-test web servers and measure their performance. It was designed to let web developers and testers measure their code under duress, to see how it will stand up to load on the internet.

Siege supports basic authentication, cookies, HTTP, HTTPS and FTP protocols. It lets its user hit a server with a configurable number of simulated clients. Those clients place the server under siege.

How does Siege help with benchmarking and regression testing:

The program reports the total number of hits recorded, bytes transferred, response time, concurrency, and return status.

Siege supports HTTP/1.0 and 1.1 protocols, the GET and POST directives, cookies, transaction logging, and basic authentication. Its features are configurable on a per user basis.

Key Features:

  • Flexibility in Testing: Siege is known for its flexibility and configurability. It allows users to simulate a variety of scenarios by specifying parameters such as the number of concurrent users, the duration of the test, and the URLs to target. This flexibility makes it suitable for a wide range of testing scenarios.
  • Support for HTTP and HTTPS: Siege supports both HTTP and HTTPS protocols, allowing users to test the performance of secure web servers. This makes it versatile for testing various types of web applications.
  • Realistic Load Simulation: Siege is capable of simulating real-world load conditions on a web server, allowing users to understand how their applications perform under different levels of stress. This realism is crucial for identifying potential bottlenecks and performance issues.
  • Detailed Reporting: Siege provides detailed and easy-to-understand reports after each test, including metrics like transaction rate, concurrency, response time distribution, and more. These reports help users analyze the performance of their web servers and make informed decisions for optimizations.
  • Support for Benchmarking Multiple URLs: Siege allows users to test multiple URLs during a single test session. This is useful for scenarios where a web application consists of various components, and the overall performance needs to be evaluated.
  • Open Source: Siege is an open-source tool, making it freely available for users to download, use, and contribute to its development. The open-source nature encourages community involvement and collaboration.
  • Cross-Platform Compatibility: Siege is compatible with various operating systems, including Linux, macOS, and Windows. This cross-platform support makes it accessible to a wide range of users regardless of their preferred development environment.

Find Siege on GitHub:

Siege - open source regression test and benchmark utility

In summary, Siege is a versatile and feature-rich tool for load testing and benchmarking web servers. Its flexibility, support for HTTPS, detailed reporting, and open-source nature contribute to its popularity among developers, testers and system administrators looking to assess and improve the performance of their web applications.

More tools in Performance Testing

Apache Bench logo

Apache Bench

Performance Testing

Apache HTTP server benchmarking tool.



Performance Testing

A flaky network simulator for your mobile app

Unlighthouse logo


Performance Testing

Scan your entire site with Google Lighthouse in 2 minutes (on average).