Pylot is a free open source tool for testing performance and scalability of web services. It runs HTTP load tests, which are useful for capacity planning, benchmarking, analysis, and system tuning.

Pylot generates concurrent load (HTTP Requests), verifies server responses, and produces reports with metrics. Tests suites are executed and monitored from a GUI or shell/console.

To begin using Pylot, read the Getting Started Guide.

How It Works

You begin by defining your test cases in an XML file. Test cases are where you specify the requests (url, method, body/payload, etc) and verifications. Server responses can be verified by matching content to regular expressions and with HTTP status codes. You can adjust the load settings in the workload controls on the GUI or from the command line before you start a test run (number of agents, request intervals, rampup time, test duration). These settings enable you to model tests based on various load scenarios. At runtime, the cases are loaded and passed to the load generating engine. Agents are dispatched and run concurrently to send HTTP requests to your web service. Real-time stats and error reporting are displayed for monitoring the test as it executes.

Who This Tool Is For

Developers, Testers, and Performance Engineers that need to test and tune the performance and scalability of their web services. It can also be used by Python programmers for integration into larger test suites. You should have a familiarity with HTTP, XML, and performance testing to use this tool successfully.


  • HTTP and HTTPS (SSL) support
  • multi-threaded load generator
  • automatic cookie handling
  • response verification with regular expressions
  • execution/monitoring console
  • real-time stats
  • results reports with graphs
  • custom timers
  • GUI mode
  • shell/console modes
  • cross-platform