Disclosed techniques relate to automatically instrumenting a web application. In an aspect, a method identifies that a web application includes an event that is triggered by a user interaction. The method associates the event with a tracer that is configured to log tracing information based on an execution of a first set of operations caused by the event and to obtain a first measurement of performance of a first span. The method identifies, in the code, that the execution of a first set of operations causes a request to be made to a server. The method associates the request with the tracer. The tracer is configured to log tracing information based on an execution of a second set of operations caused by the request and to obtain a second measurement of performance of a second span that is a child span of the first span.