Edit: Thanks for the feedback, I didn't know some of these (like VWO) were of Indian origin.
In addition to what linux_devil has mentioned, on the enterprise side there is Plivo, HackerRank, FreshDesk, Helpshift, Druva, RecruiterBox, Webengage, VisualWebsiteOptimizer etc.
flipkart , olacabs , snapdeal , zomato ,etc. are also there , but it's definitely one of the leading ones