Techniques for code modification for automation detection are described. Web code is obtained corresponding to content to be served to a first client device in response to a first request from the first client device. Instances of a particular programmatic element in the web code are identified. In response to the first request, modified web code is generated from the web code by consistently changing the particular programmatic element to a modified programmatic element throughout the web code. The modified web code is caused to be provided to the first client device in response to the first request from the first client device. A communication is received from the first client device that is made in response to the modified web code. The communication includes an attempt to interact with the particular programmatic element that exists in the web code but not in the modified web code.