As per G2 Crowd, one of the best review websites. Here I am listing the best alternatives for BrowserStack.
CrossBrowserTesting is a cloud testing platform that gives instant access to 1500+ different real desktop and mobile browsers for testers, developers, and designers.
Improve the quality of your iOS, Android, and web applications by testing against real phones and tablets in the AWS Cloud.
UserTesting’s Human Insight Platform enables companies to see, hear and talk to their customers as they engage with products, apps and messaging. Half of the world’s top 100 brands partner with UserTesting to make more informed decisions based on customer feedback.