Apache JMeter is an open-source desktop and command-line application for load testing and measuring the performance of software. Originally built for web applications, it now covers many protocols, including HTTP and HTTPS, SOAP and REST web services, FTP, databases via JDBC, LDAP, JMS, mail protocols and TCP. A graphical interface supports recording, building and debugging test plans, and a headless command-line mode runs them on any Java-compatible system. JMeter works at protocol level: it is not a browser and does not execute JavaScript. It is a pure Java application that you download and run yourself.
JMeter is a project of the Apache Software Foundation, a US 501(c)(3) non-profit, and Apache projects are released under the Apache License 2.0. Because JMeter runs on your own machines, there is no vendor-hosted service, and test data stays in your environment unless you send it elsewhere. For a European organisation this means full control over where tests run and where results are kept, with the operating effort that self-managed open source entails.