A browser can include a script monitoring module to monitor executing scripts and log the initiating scripts for API calls or other monitored actions. In some embodiments, the script monitoring module overwrites built-in or web APIs in the browser with versions of the APIs that allow the script monitoring module to identify the scripts calling the APIs. Using the script monitoring module, the script initiating an action (such as an API call) can be identified using features of the browser. In some embodiments, all actions may be monitored in this way, permitting the tracking and analysis of scripts and full analysis of interaction between such scripts on the webpage and with the browser.