Postman - The Collaboration Platform for API Development
Dynatrace Load - Dynatrace Load lets you test the performance of web and mobile applications with the realism of load generation from the cloud.
Sauce Labs - Test mobile or web apps instantly across 700+ browser/OS/device platform combinations - without infrastructure setup.
Apache JMeter - Apache JMeter™.
TestComplete - TestComplete Desktop, Web, and Mobile helps you create repeatable and accurate automated tests across multiple devices, platforms, and environments easily and quickly.
Sitespeed - Sitespeed.io is an open source tool that helps to analyze and optimize website speed and performance.