Web server performance testing is crucial for ensuring that a website or web application can handle high traffic loads without crashing or slowing down. There are several tools available that can help developers and IT professionals gauge the performance of their web servers and make necessary improvements. Here are the top 13 web server performance testing tools:

1. Apache JMeter: Apache JMeter is a popular open-source tool for testing the performance of web servers. It can simulate heavy loads on a server to measure its performance under various conditions.

2. LoadRunner: LoadRunner is a performance testing tool developed by Micro Focus that can simulate thousands of users accessing a web server simultaneously. It can help identify bottlenecks and performance issues.

3. Gatling: Gatling is a high-performance load testing tool that is designed for developers. It uses a Scala-based scripting language to create performance tests for web servers.

4. WebLoad: WebLoad is a load testing tool that can simulate user activity on a website to measure its performance under different scenarios. It can help identify performance issues, such as slow response times and crashes.

5. LoadNinja: LoadNinja is a cloud-based load testing tool that can simulate real user interactions on a website. It can help identify performance issues and optimize web server performance.

6. NeoLoad: NeoLoad is a load testing tool that can simulate thousands of users accessing a website. It can help identify performance bottlenecks and optimize web server performance.

7. BlazeMeter: BlazeMeter is a load testing tool that can simulate heavy loads on a website to measure its performance under different conditions. It can help identify performance issues and optimize web server performance.

8. Locust: Locust is an open-source load testing tool that can simulate heavy loads on a website. It is easy to use and can help identify performance bottlenecks and optimize web server performance.

9. LoadImpact: LoadImpact is a cloud-based load testing tool that can simulate user activity on a website. It can help identify performance issues and optimize web server performance.

10. Artillery: Artillery is an open-source load testing tool that can simulate heavy loads on a website. It is highly flexible and can help identify performance issues and optimize web server performance.

11. Rational Performance Tester: Rational Performance Tester is a performance testing tool developed by IBM that can simulate heavy loads on a website. It can help identify performance bottlenecks and optimize web server performance.

12. Siege: Siege is an open-source load testing tool that can simulate heavy loads on a website. It is easy to use and can help identify performance issues and optimize web server performance.

13. Loader.io: Loader.io is a cloud-based load testing tool that can simulate heavy loads on a website. It can help identify performance issues and optimize web server performance.

In conclusion, web server performance testing is essential for ensuring that a website can handle high traffic loads without crashing or slowing down. The above-mentioned tools can help developers and IT professionals gauge the performance of their web servers and make necessary improvements to optimize performance.