Discover 10 Free Tools to Load‑Test Your Web Applications

This article lists ten free tools you can use to perform load or stress testing on web applications, allowing you to determine how many concurrent users your server and site can handle and evaluate performance.

0. Grinder – Grinder is an open‑source JVM load‑testing framework that provides distributed testing via many load injectors. It supports a Jython script engine for test scripts, and HTTP testing can be managed through an HTTP proxy. According to the project site, Grinder’s main target users are programmers who want to understand the code they test; because the test process can be coded rather than merely scripted, developers can test internal layers of an application, not only UI response times.

1. Pylot – Pylot is an open‑source tool for testing web service performance and scalability. It runs HTTP load tests useful for capacity planning, establishing baselines, analysis, and system tuning. Pylot generates concurrent HTTP requests, checks server responses, and produces metric reports. Tests can be executed and monitored via a GUI or a shell/console.

2. Web Capacity Analysis Tool (WCAT) – WCAT is a lightweight load‑generation utility that can replay scripted HTTP requests against a web server or load‑balancer and collect performance statistics for later analysis. It is multithreaded, can control many client machines from a single source, and can simulate thousands of concurrent users. WCAT supports HTTP 1.0 or 1.1, SSL, basic or NTLM authentication, cookies, forms, and session‑based authentication.

3. fwptt – fwptt is a tool for web application load testing. It can record normal requests as well as Ajax requests and can be used to test ASP.NET, JSP, PHP, or other web applications.

4. JCrawler – JCrawler is an open‑source Java web‑application stress‑testing tool that works like a web crawler. Given a few URLs, it crawls them and generates load in a special way. It can also build a site map and automatically submit it to the top five search engines.

5. Apache JMeter – Apache JMeter is a pure‑Java desktop application designed for load testing servers and applications. Originally for Web/HTTP testing, it now supports many test modules, including HTTP and JDBC for databases. It can test static or dynamic resources, simulate heavy load, analyze performance under different loads, and provides a customizable interface for data display, test synchronization, and execution.

6. Siege – Siege is a stress‑testing and benchmarking tool for web development that evaluates how an application behaves under load. It can perform concurrent access to a web site, record response times for each request, and repeat the test under a specified number of concurrent users. Siege supports basic authentication, cookies, HTTP and HTTPS.

7. http_load – http_load runs in parallel multiplexed mode to test web server throughput and load. Unlike many tools, it runs as a single process and typically does not overwhelm the client machine. It can also test HTTPS sites.

8. Web Polygraph – Web Polygraph is a performance testing tool used by many companies, including Microsoft, as a benchmark for software performance. It is a standard tool mentioned in many job ads for performance testers.

9. OpenSTA – OpenSTA is a free, open‑source web performance testing tool that records powerful scripts, executes performance tests, and can simulate multiple users logging into a site simultaneously. Scripts can be edited with a specific syntax for detailed performance analysis. It provides rich graphical results, uses a CORBA‑based architecture with a proxy, records all HTTP/S traffic, and collects performance metrics for analysis.